======Navigator's Tools======
The role of a ship's navigator is a big one that involves a lot of
moving pieces. A navigator must procure detailed maps, map
out the voyage of the ship, keep in mind the weather and its
effects on the voyage, keeping detailed notes on the journey
and be able to deduce the ship's position while out at sea.
=====Navigator's Tools=====
Navigator's tools include a sextant, a compass, calipers, a
ruler, parchment, ink, and a quill. Proficiency with this kit
allows you to add your proficiency bonus to any checks you
make for creating or studying maps.
The tools weigh 2 lbs and cost 25 gp.
=====Navigation=====
The Navigator's role is for plotting courses, determining your location on the open seas and determining how the weather will affect your voyage. Without a navigator, a ship is more likely to become lost at sea and is unable to prepare itself for the harsh weather that races quickly across the waves. 

This is assuming you are using the rules laid out in the
Dungeon Master's Guide for D&D 5th Edition, though this
can be easily adopted to any travel system. Furthermore, there
are more options for Navigators/Quartermasters in the
Ghosts of Saltmarsh adventure book or the Of Ships and
Seas - Unearthed Arcana.

=====Weather Forecast=====
One of the main jobs that a Navigator is responsible for is
ensuring that the captain of the ship is apprised of any foul
weather on the horizon and plotting a course to help steer
around it. By taking an hour, which can be done during a short
rest, the Navigator can study the skies, the ocean currents and
take a feel for how the atmosphere feels around them, then
they can make a Navigator's Tools (Wisdom) check to
determine what the weather will be like for a number of days
based off of their result.

Furthermore, they can determine how far out the weather is
in the hexes surrounding them. In this chart it is assumed the
Hexes are 60 miles wide and is at a Continent Scale, see page
14 in the Dungeon Master's Guide for more information on
map sizes.

^ Number of Days Out ^ Navigator DC ^ # of Hexes Out* ^
| Current | 10 | Current Hex (60 miles) |
| Next Day | 12 | 1 (180 miles) |
| Next 3 Days | 15 | 1 (180 miles) |
| Next 5 Days | 18 | 2 (300 miles) |
| Next 7 Days | 20 | 2 (300 miles) |
*Hex size is assumed to be 60 miles wide and on a Continent Scale map.

=====The Weather=====
The weather can be treacherous when sailing across the
ocean, and its important to know what is coming. Different
types of storms and their effects on your ship can be found on
the next page.

=====Plotting a Course=====
At the beginning of each day at sea, you must plot out your
course for the day. By spending an hour with your charts and
plotting out the direction of your ship, you can ensure that you
end up where you are expecting to, even when the weather is
trying to throw you off.

The DC for plotting a course depends on where you are in
relation to land and whether you are traveling through
uncharted territory or have a map, the DC is determined
based on your position in the morning though the DM might
call for a second check that night if you have significantly
changed your location, per the DM's discretion.
When you plot your course in the morning, you must roll a
Navigator's Tools (Wisdom) check against the DC.
====Plotting DC====
^ Location ^ DC ^
| Within sight of land, with a map | 10 |
| Within sight of land, no map (staying near land) | 11 |
| In charted waters, with a map | 10 |
| In charted waters, no map | 13 |
| In uncharted waters | 15 |
| Supernatural waters | 18 |
====Becoming Lost====
If you become lost while traveling out at sea, you can spend an
hour that night determining your location with the help of the
stars, if they can be seen. If you are in a bad storm, heavy fog
or some other reason you can not see the stars, you are
unable to make this check.

You must succeed on a Navigator's Tools (Wisdom) check
versus the DC of your location (per the Plotting DC chart
above). Upon successfully making the check, you are no longer
lost and you can find yourself on the map. You can repeat this
check at the end of every day you are lost.

If you are proficient in Survival checks, you can double your
proficiency bonus for this check.
====Assisting====
While you are plotting out your course, you can gain
advantage if someone else is proficient with Navigator's Tools
or is proficient with the Cartographer's Tools. If you are
proficient in both tools, you can instead double your
proficiency to any Navigator's Tools checks for plotting a
course so long as you have both tools on you and you have
been working on your maps every day.

====Weather====
^ Type ^ d100 ^ Effect ^
| Typhoon | 1-2 | You are inside a storm that will be raging for 1d3 days. While in the Typhoon you are considered Lost while traveling and make no progress in the day, and must wait out the storm. Every day you are in the Typhoon, the ship must make a DC 12 Constitution check or take 6d10 bludgeoning damage to their hull and sails. On a successful save, the hull and sails takes half damage. Visibility is is heavily obscured and after the Typhoon subsides, you are Lost and must roll on the Blown Off Course chart. |
| Gale Winds | 3-7 | Strong winds threaten to blow you off course. For 1d4 days the Navigator has disadvantage on their Navigation checks. If they fail at least one of their checks, they are Lost and must roll on the Blown Off Course chart. Furthermore, if they choose to not take the sails down, than the ship must succeed on a DC 10 Constitution Saving Throw or take 3d6 bludgeoning damage to the Sails. Visibility is not affected. |
| Storms | 8-17 | The Ship is rocked heavily by storms for 1d6 day and the Navigator must make a DC 12 Constitution saving throw or become wracked with seasickness and have disadvantage on their Navigation checks for the day. Visibility is heavily obscured. |
| Heavy Fog | 18-25 | Heavy Fog obscures all visibility for 1d6 day. The Navigator has disadvantage on their Navigation check. |
| Inclement Weather | 26-30 | Poor weather limits visibility and your vision is lightly obscured for 1d4 days. |
| Calm Winds | 31-34 | The winds that help move your ship along have gone quiet, forcing you to pull out the oars. For the next 1d4 days, the winds are stilled and you must rely on your oarsmen to pull the boat forward. |
| Ill Favored Winds | 35-39 | Powerful winds blow against you, reducing your speed against them for 1d4 days. |
| Favorable Weather | 40-95 | All is right with the seas, and you have 1d10 days of normal weather. |
| Strong Winds | 96-100 | You have found a favorable wind and it propels you along for 1d4 days increasing your speed if you use your sails. |