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People have been going into the water for a long time – one very speculative theory claims that many human traits are adaptations to a partially aquatic lifestyle! Mankind’s most notable adaptive mechanism is technology. This has certainly played a major role in our activity on the water, in forms ranging from inflated leather floats through sailboats to nuclear-powered warships. While it’s unclear when such innovation began, Paleolithic societies were island-hopping on rafts or canoes 30,000 years ago, and improvised floats could be even older.

Even before boats, early man developed aids to swimming, or to crossing water in other ways.

Floats are the starting place for all watercraft. A float is any small object, lighter than water, which a swimmer can hold onto or fasten to his body for added buoyancy. Its buoyancy subtracts from the user’s encumbrance, and if buoyancy exceeds encumbrance, the float gives a Swimming skill bonus equal to (excess buoyancy/swimmer’s weight) x 8, rounded down, to a maximum of +8. Floats don’t improve swimming speed. Indeed, they may reduce it by increasing water resistance or by occupying the arms to such an extent that the user has limited mobility.

Floats can vary greatly in construction, and be of any size. Some are solid blocks of a material that’s less dense than water; others are hollow, and get their buoyancy from the air they contain. Most can be described by their buoyancy, weight when carried on land, and cost – all given per cubic foot (cf) here. Buoyancy and weight sum to 62.5 lbs. per cubic foot (the density of water).

Logs: It’s convenient to figure a log’s statistics from length rather than volume. For a 12”-diameter log, buoyancy is 25 lbs., weight is 25 lbs., and cost is $6 – all per foot of length. For other diameters, multiply these three figures by the square of (diameter/12”); e.g., a 6”-diameter log has a multiplier of 0.25, making buoyancy and weight 6.25 lbs., and cost $1.50, per foot.

Instead of clinging to a log while floating in the water, one can sit astride it or even stand on it. Of course, the log may roll over! Straddling a log, roll vs. DX at +4 to complete your journey without getting dunked; make one additional roll per stretch of rough water encountered. Standing on a log, these rolls are against unmodified DX. Walking carefully along the log at Move 1 requires no additional rolls – but if running any faster, roll every second. Perfect Balance gives +6 to all these rolls.

The surfboard was developed in Hawaii before European contact. There, riding the waves was a sport for chiefs, comparable to jousting for medieval Europeans. Surfing uses the Sports (Surfing) skill. Speed on the best waves might reach Move 12-15, but paddling is seldom faster than Move 1. A nobleman’s board (15’x18”x5”): $100, 150 lbs. A commoner’s board (smaller, averaging 10’ long): $75, 100 lbs.

A fourth-century Roman military text describes this contraption as the ascogefyrus. Skins are worked to form flattish air sacs instead of round ones, inflated with bellows, and rolled up and carried to a river, where they’re unrolled and tied into place. Unrolling takes a second per yard and produces a 4’-wide walkway. Footing is unreliable; use the rules under Rafts (below). Buoyancy is 720 lbs./yard, but the top can only support 310 lbs./yard without buckling. Per yard: $200, 30 lbs.

A raft consists of floats of any kind lashed together with ropes or thongs. The result is a flat surface for passengers to stand on. Individual floats may be solid or hollow, but the raft gets all its buoyancy from their lightness – it has no interior space.

A raft’s surface flexes with the water beneath it or the shifting of its load. Roll vs. DX at -4 to move around or at -2 to stand in place. Combat is at -4 to attack and -2 to defend for bad footing. A raft made from logs or reasonably long reed bundles only flexes in one dimension; halve all these penalties. One held together rigidly with wooden crosspieces, pegs joining adjacent logs, or very tight cords causes combat penalties only (still halved, if made from long pieces); make rolls for balance only if the whole raft shifts because of water turbulence or large waves, and use unpenalized DX. Perfect Balance grants +6 to these DX rolls.

The Rafts Table describes two-yard-square sections of raft; for bigger rafts, assume multiple sections of this size. One section provides footing for up to four people, but is crowded for more than one; in a fight with two combatants, the loser may go over the edge! The specified load has the top of the raft barely above the waterline, with low waves washing over it; cutting the burden by 50% gives freeboard equal to 25% of the raft’s thickness.

Rafts often simply drift with water currents. They can be propelled in shallow water by poling with a wooden pole from 12’ to 20’ long. The pole must be held at an angle to produce horizontal thrust, so the maximum depth of bottom that can be reached is 85% of pole length. Poles can also be used to fend off obstacles. At TL1+, a raft may have a square sail.

Unlike boats and ships, which have complex structures and are treated as Unliving, rafts are considered Homogenous.

Terms and notation are as defined in Vehicle Statistics (pp. B462-463).

Where a raft works like a solid float made of light material, a boat functions as a hollow float that gains buoyancy from its air content. Typical boats have interior spaces open at the top, with the water kept out by walls that rise above the water level.

At TL0, boats are normally made from a single piece of material. This may be a solid object that has been painstakingly hollowed out (such as a dugout), or it might consist of something flat that has been shaped to enclose an interior space, usually with some sort of framing (e.g., a bark canoe or a skin boat). Ceramic vessels large enough to serve as boats, used in parts of India, are TL1; they’re too breakable for rocky or fast-moving streams, and none are described here.

The major change at TL1 is the development of the plank boat, such as the European rowboat or East Asian sampan. Where TL0 craft can’t easily be enlarged beyond the limits of the material, TL1 designs add planks to build up the sides. This allows scaling up to much larger craft, from wider boats to full-scale ships (for big ships, see GURPS Low-Tech Companion 2 and 3).

Propulsion for boats at TL0 involves poling or paddling, or occasionally improvised towing methods. The more efficient technology of rowing is TL1. Paddling uses only the arm muscles; in rowing, the oarsman can brace against a seat within the boat, letting him use his full body strength. A less common technique is single-oar sculling, in which a large oar that pivots at the stern – such as a yuloh (from Chinese yaolu) – is swept from side to side. Use of harnessed draft animals for towing also starts at TL1.

The most important TL1 innovation, however, is the sail – initially in single-masted craft, usually with square sails that are best-suited for running before the wind (although the Polynesian proa design can sail into the wind quite efficiently). Vessels with small auxiliary sails emerge at TL2, as do early fore-and-aft rigs, which are more capable of sailing into the wind. By TL4, craft may have three or four masts, and ships with two or more masts can be full-rigged, combining square and triangular sails to great effect.

Warships up through TL3 find sails too unreliable. Two important TL2 developments are multiple rows of oars down each side of a ship (as in the trireme) and multiple men working the same oar (as in the quinquereme and, later, in Byzantine warships). Variants on both designs remain in use into late TL3. At TL3, the Chinese experiment with paddlewheels powered by men on treadmills (see GURPS Low-Tech Companion 2).

Boats at TL0 are steered with a paddle dipped into the water at the stern. At TL1, this evolves into the permanently attached steering oar. Ships at TL3-4 usually have rudders, attached at two points rather than one, so that they can be rotated around a vertical axis. Early European ships have single or paired side-mounted rudders; later European ships, and most Chinese junks, have one rudder mounted at the ship’s rear, on its midline.

A bark boat, or canoe, is made from a single piece of bark taken from a tree whose bark can be stripped off in large sheets; e.g., birch, elm, or hickory in North America, eucalyptus in Australia, or spruce in North America and Scandinavia. This is bent into a semi-cylinder with width between 1/8 and 1/5 of length, with its ends curving up. Then the ends are sealed, usually by sewing them up – although improvised boats may have the ends blocked off with grass and clay, or simply bent up out of the water. Such vessels are speedy but unstable. Most have some internal framing to hold their shape, but not enough to support oarsmen; they’re usually propelled by paddling. Construction is very light, with walls averaging just half an inch thick.

Large Bark Canoe (TL0). A large but comparatively light canoe, 20’ long and 3’ wide, that holds four men seated in a single row.

Voyageur Canoe (TL4). A distinctive, very large bark canoe used for trade in Canada after European contact. The body is 35’ long and 5’ wide, and holds 14 paddlers seated side by side in seven pairs, plus a steersman and 4 tons of cargo. The construction, influenced by European boatbuilding traditions, is sturdier than for traditional canoes.

Animal-skin boats have been in use since the Stone Age in area without large trees, including arctic, desert, and plains environments, and rocky regions like western Ireland. Skins are stretched over a light wooden frame that gives them a definite shape, chosen by the builder; this may be anything from a nearly circular coracle to a narrow kayak with two pointed ends. Construction is extremely light – one man can carry a small hide boat. These vessels are usually paddled; the frame isn’t rigid enough to support oarlocks. A variation on this design is a circular or oval boat with a basketry frame. It’s made watertight by stretching hides over the frame or by sealing it with tar – in Mesopotamia, for example, thanks to its petroleum deposits.

Kayak (TL0). A one-man watercraft used by Inuit hunters; the Siberian baidarka is similar. The design is fast and maneuverable, with a long, narrow body, traditionally three times the owner’s height (15’-18’) and no more than 27” wide. The deck is roofed-over and the rider’s torso protrudes through a narrow opening, which fits too tightly for water to enter. Kayaks are famously easy to right if capsized; this calls for a Boating (Unpowered) roll at -3. Propulsion comes from a double-ended paddle. Made of sealskin framed with wood or whalebone, the vessel is light enough for one man to carry. A few kayaks have two or even three seats.

Oblong Hide Boat (TL0). Comparable to the Irish coracle, this craft is fairly round but somewhat longer than it is wide. Use the same statistics for Vietnamese fishing boats made of bamboo matting and sealed with resin. Typical dimensions are 5’ long and 2/3 as wide. Propulsion is by paddling.

Round Hide Boat (TL0). A circular watercraft made of hides with a light wooden frame, such as the Plains Indian bull boat or the bamboo-framed parical of South India. The Mongols used a similar boat, called pi in Chinese. Use the same statistics for the ancient Mesopotamia quffa (TL1), made of basketry with an external coat of tar. The boat on the table is 5’ in diameter.

Large Hide Boat (TL1). A craft framed with substantial timbers and covered with several large hides, such as the Inuit umiak, the similar Siberian baidara, or the Irish currach (used into modern times – and the vessel in which legend claims St. Brendan made his voyages over the Atlantic Ocean). These craft are “boat-shaped,” with curved sides, steered by an oar at the stern, and propelled with oars or a sail. Typical dimensions are 36’ long, 6’ wide, and 3’ high.

A basic log boat, or dugout canoe, is made by taking a large tree and hollowing it out with fire or cutting tools, leaving a roughly U-shaped rigid shell. Such a vessel is much heavier than a bark canoe, with walls averaging 2”-3” thick. It’s also more seaworthy; the ancient Polynesians crossed the Pacific Ocean in craft like this. Log boats can be produced wherever good-sized trees grow.

There are ways of increasing a log boat’s size that don’t work for a bark canoe. It can be extended by joining two logs end to end. It can be expanded by using hot water, hot oil, or smoke to soften the wood and then bending the sides outward. And it can be built up by adding a board along each side – a first step toward a plank boat (below). A dugout can also have a second log parallel to the first, yielding either a comparatively small outrigger canoe or a full-scale double canoe; both designs are common around the Pacific.

Dugout Canoe (TL0). A very basic log boat, suitable for one man, made from a log 8’ long and 2.5’ in diameter. Long Dugout Canoe (TL0). A basic dugout made from a bigger log, 30’ long and 3’ in diameter. It can accommodate more paddlers for its length by placing them alternately on the left and right sides, taking advantage of its width.

Outrigger Canoe (TL0). A long dugout canoe equipped with an outrigger: a smaller log, 15’ long, attached to its midsection by several 3’ poles. This provides added stability in the water. Such craft are well-suited to lengthy ocean voyages, such as the Polynesian expansion through the Pacific Ocean. The outrigger is designated R, like a runner or skid, on the Boats and Ships Table – and like those components, is treated as vehicle hit location 15-16.

War Canoe (TL0). A very large dugout canoe, such as the Maori war canoe of New Zealand, carved from a single kauri pine whose sides are expanded to provide room for two paddlers side by side. Its length is 60’ and its beam 5’. Similar craft are found in the Pacific Northwest; in areas with smaller trees, they may be made by joining two trees end to end. Treat war canoes as LC1.

Double Canoe (TL1). This sailing vessel is similar to those used by the Polynesians who colonized the Pacific. Two long dugout canoes are held side by side, 10’ apart, by a frame that supports a mat platform 15’ square. Above this is a mast bearing a proa sail, a distinctive design that can be used to beat upwind by shunting (see Sailing Against the Wind, p. 141). There’s room for half a dozen paddlers in front of the platform and behind it; the portion of the canoes that’s under the platform is used for storage. The two canoes together make up the craft’s body; if an attack could hit either, assign it randomly to one or the other. If one canoe leaks, the craft may be threatened by tipping.

The first vessels made entirely of planks had one bottom plank and two side planks. The East Asian sampan – meaning “three boards” – was of this type. Larger boats, and eventually ships, could have many side planks rather than just one per side.

Plank boats can be any shape that has a definite fore and aft. Barges have rectangular hulls with straight sides; other craft have curving sides. Bow and stern may be pointed, rounded, squared-off, or “boat-shaped” (pointed in front and squared-off at the rear). The bottom may be flat, rounded, or V-shaped. Cargo carriers are commonly rounded or rectangular, to give them more interior space; warships tend to be narrow, with pointed prows and Vshaped bottoms, for better speed.

The simplest designs are nothing but shells made from planks, either edge-joined or overlapping (“clinker-built”). Planks can be held together by sewing, wooden pegs, or metal nails (mainly at TL3+). Waterproofing comes from the shell’s tight fit. In larger plank boats, adding an internal frame can increase structural strength – partly by preventing the craft from flexing into shapes that strain the hull.

At TL3, a radically different approach emerges: building the frame first, fastening the hull timbers to the frame, and then caulking in between to waterproof the vessel. The heavier framing of plank boats lets them carry oarsmen, or support one or several sails on masts. Small auxiliary masts were introduced on Roman ships at TL2. Two and three-masted ships came into use in Europe at TL3 – and the Chinese in the same period built junks with as many as nine masts!

River Barge (TL1). A fairly large, flat-bottomed, rectangular vessel suited to hauling bulk cargo up and down river, or ferrying freight and passengers across a river. This is effectively a big open box, 40’ long, 7.5’ wide, and 1’ high, very slightly tapered toward the ends. As a ferry, it’s poled by four men on each side; the table entry assumes this. For travel up river, it must be towed.

Sampan (TL1). This is the starting point for East Asian boat and ship design: a flat-bottomed boat made from one bottom plank and two side planks. Typical dimensions are 15’ long, 4’ wide, and 1.5’ high. The side planks converge in front in a pointed prow; the stern is squared-off. The craft has one advanced design feature, thought to have been inspired by the structure of bamboo: bulkheads divide its interior into several watertight segments, making it very hard to sink. Propulsion is normally single-oar sculling with a yuloh; in shallow waters, it can be poled.

Sewn-Plank Riverboat (TL1). A boat in the Egyptian style, assembled from planks of acacia (or expensive imports such as cedar) averaging 3’ long, sewn together edge to edge. Dimensions are 30’ long, 7’ wide, and 2.5’ high. Both ends taper to points. It’s usually propelled with paddles wielded by four pairs of crewmen. A lookout on the bow uses a sounding pole (p. 52) to feel for snags, while a helmsman in the stern steers with a paddle held in the water.

Fishing Boat (TL2). A boat constructed in the shell-first style of the ancient Mediterranean, with planks joined edge to edge and pegged together. Construction is light, with minimal framing. Dimensions are 27’ long, 7.5’ wide, and 4’ high; the bow is pointed, while the stern is squared-off. Propulsion is by two pairs of oars. Primarily used for fishing, but can be adapted to carry cargo or up to 10 passengers.

Square-Rigged Sailboat (TL2). This is a Romano-Celtic craft of the British Isles under the later Roman Empire. Its planks are laid edge to edge, but not fastened together.; rather, they’re nailed to framing timbers, and the gaps are caulked. Dimensions are 37.5’ long, 10’ wide, and 3’ high; both bow and stern are pointed. A single 25’ mast a third of the way back from the bow holds a square sail. Construction is sturdy enough for use in bays and coastal waters.

Faering (TL3). A boat constructed much like the squarerigged sailboat (above), but with 3-4 pairs of oars, used in the Viking era – although the same stats can represent a variety of medieval oared boats. Typical size is 20’ long, 4’ wide, and 2’ high. It can be used in coastal waters for fishing or transport, or as a tender for a larger ship.

Sewn-Plank Sailboat (TL3). A boat of the design traditionally used in the Indian Ocean, with long planks stitched together, and little or no frame. The hull’s flexibility is actually an advantage for operating in coastal waters. A single mast carries a large lateen sail, which is efficient for sailing into the wind but too heavy for tacking; instead, the ship relies on wearing (see Sailing Against the Wind, p. 141). At 22’ long and 5’ wide, this craft is comparatively small, and suited for fishing or local travel.

Brig (TL4). This two-masted sailing vessel carries square sails – a configuration that requires a larger crew to handle the sails than on a fore-and-aft rigged ship (such as the sloop, below). The example in the table is fairly small: 50’ long, 18’ wide, and 10’ from top to bottom. Its sail configuration is best suited to long sea voyages running before the wind; it’s less efficient for beating upwind, and thus not ideal for working in close to shore.

Rowboat (TL4). Not a specific vessel but a broad category of European boats – all propelled by a small number of oarsmen, and built with overlapping planks, pointed prows, and flat sterns. The table offers two examples. The longboat is 30’ long and 4.5’ wide, with four pairs of rowers and a coxswain; it was used between 1515 and 1867 as a ship captain’s boat. The jolly boat is 18’ long and 4’ wide, with three pairs of oarsmen, and used as a ship’s small utility boat, customarily lowered off the stern.

Sloop (TL4). A one-masted sailing vessel, developed in the Netherlands in the early 1600s. The mast is placed in the craft’s forward third, and carries two triangular foreand- aft sails, giving it the classic triangular “sailboat” silhouette. The one in the table is comparatively small: 21’ long, 7’ wide, and 6’ high. A 3’ bowsprit gives added sail area. Good maneuverability and the ability to sail close to the wind make this design useful to adventurers; larger sloop-rigged ships were favored by pirates. A cutter is similar, with the mast further aft.

Many sailboats can travel in a direction opposite to that in which the wind is blowing. If the sail is parallel to the wind rather than across it, then as the wind blows past, it generates aerodynamic lift that pushes at right angles to it. If the boat has a keel (or the equivalent, such as a canoe’s long body or a junk’s deep rudder), setting the sail at an angle to the hull means that the part of the thrust that’s directed along the hull propels the ship, while the component that’s directed sideways has little propulsive effect. Rather, it makes the ship heel over. No ship can sail straight into the wind; it must always sail at an angle to the airstream. Holding a steady course into the wind necessitates zigzagging back and forth, putting the wind alternately to port and starboard. There are three different methods of doing this:

• Wearing is turning to sail away from the wind, and then looping around to sail upwind at the opposite angle, so that the ship turns through roughly three-fourths of a circle, tracing a series of loops. This is the only method of beating upwind available to square-rigged ships.
• Tacking is turning the ship’s prow straight into the wind, losing speed while doing so, but then continuing the turn until the wind is coming from the other side.
• Shunting is turning to face at right angles to the wind, and then turning the sails completely around to sail the ship stern-first, pointing the stern into the wind. This requires a hull that’s pointed at both ends, as in Polynesian canoes. The sail is turned by picking up and rotating the entire mast.

Strictly speaking, a reed “boat” is a kind of raft – it has no hollow interior, but floats because its material is lighter than water. It’s called a boat because of its shape (oblong or pointed) and the way it handles in the water. Reed boats become waterlogged with use; tight binding of the reed bundles prolongs their useful life. Small, tapering logs can be bound together to form comparable watercraft. Reed boats made from papyrus were common in early Egypt. The top surface was sometimes covered with planks to give better footing; historians speculate that this development may have been a step toward boats made entirely of planks. The unusual Egyptian wishbone mast – attached to either side of a boat’s hull – might have been developed for use with reed boats, which had no keel to provide a stable attachment point. Comparable boats were used in other parts of Africa, Brazil, and similar tropical areas.

Fowling Boat (TL1). A papyrus raft boat built for pharaohs and nobles to use for duck hunting along the Nile, suitable for travel over still or slow-moving water anywhere. The 16’-long body tapers from a 3’ beam at the midsection to a blunt prow and a sharp stern, both curved up out of the water. Two crewmen pole the craft, while a passenger rides up front.

Terms and notation are as defined in Vehicle Statistics (pp. B462-463).

The ocean’s depths were a mystery to preindustrial societies. Divers could go a few yards underwater, and stay down for a minute or two. Human inventions extended some of these limits, but only added marginally to attainable depth.

These items let a diver go deeper, or stay underwater for longer than he can hold his breath.

The human body weighs nearly the same as an equal volume of water. Reaching any significant depth quickly requires either jumping in from a height or actively swimming downward. An early solution to this difficulty is a stone with a cord tied around it. The diver thrusts one foot into the cord, as through a stirrup, and is carried down at Move 1 without active effort. He can move horizontally at the same time by making a Swimming roll at -1. To allow reuse, tie the stone to a length of rope that a companion in a boat can use to pull it up. $5, 15 lbs.

Ancient Egyptian fowlers developed an early snorkel analog to help them sneak up on waterfowl: a papyrus reed used like a huge straw to inhale air while submerged. A 2’ tube allows submergence 16” below the water. Any deeper and water pressure prevents the lungs from taking a breath. Observers are at -2 to Vision to spot the swimmer. $5 (or free, with a Naturalist or Survival roll), 0.5 lb.

An Assyrian relief dated to the eighth century B.C. shows divers using air-filled animal skins to prolong their dives. The bladders are inflated before the diver enters the water, and provide several breaths’ worth of air. Multiply the times under Holding Your Breath (p. B351) by four when using an air bladder. It also acts as a float (p. 138), so the diver must carry additional weight (60 lbs.) to remain submerged. $15, 2.5 lbs.

In 1620, Cornelius Drebbel, a Dutch experimenter living in England, designed and built the first known submarine for the Royal Navy. It worked well enough that he constructed two more, larger models. In 1624, James I rode in the last one on a test dive under the Thames. The navy wasn’t impressed enough to use it in combat, but later experimenters could have copied the design.

The diving boat is basically a 15’ rowboat with a roof, covered with greased leather. Six pairs of oars protrude through leather gaskets to supply thrust. As it uses oars rather than a propeller, operating it requires the new Unpowered specialty of the Submarine skill (p. 11). Buoyancy control is handled by filling bladders under the rowers’ benches to submerge, and squeezing out the water to surface. Metal ballast supplies extra weight to make up the full load of 3.2 tons needed for neutral buoyancy. The boat can submerge to 15’; the longest recorded trip took 3 hours. Air tubes attached to floats enable crew and passengers to breathe. Some accounts claim that Drebbel invented an “alchemical” means of keeping the air breathable, though. The GM may choose to give the diving boat TL(4+1) rebreather technology.

Terms and notation are as defined in Vehicle Statistics (pp. B462-463).