So, a while ago I created a pirates RTD, for which I designed a couple rudimentary systems. That game has since sunk, but why let those systems go to waste? Let's take those and build upon them
Here's our starting point:
Resource System:
-Every crew member consumes 1 unit of food and 1 unit of water per day, by default, but might choose to forgoe for whatever reason
-Barrels hold 20 units each
-For every day without food or water, a crew member gains increasing penalties. After 3 days without water, the crew member must roll against dehydration with increasing DC or die. After 10 days without food, the crew member must roll against starvation every day with increasing DC.
-Some food items are perishable, days to spoil depends on the item. Meats can be preserved with 1 unit of salt per 5 of meat.
-Booty/money/treasure gives bonuses to purchase rolls
-Ammunition is tracked
Encounter/Travel System:
-Travel mode: days to reach a destination depends on distance and ship speed.
-For every day of sailing that passes, supplies are deducted and a roll for encounter is made
--First, roll to see if there is an encounter
--If there is an encounter, several rolls to see what it is from the encounter table/tree
--Encounters include such things as merchant ships, civilian ships, other pirate ships, Navy ships, plague ships, monster-infested ships, ghost ships, wrecks, derelicts, sea monsters, reefs/other hard to see obstacles, and inclement weather (though weather might need its own system)