Skulls and Shackles
It is assumed that after combat, a number of enemy crew or villagers join the PCs’ crew to replace any losses.
Additional new crew members may be recruited after successfully capturing an enemy vessel or raiding a village, or any time the ship is docked at a port.
To do so requires one PC to make a DC 20 skill check: Bluff (to trick sailors on board), Diplomacy (to convince people to join the crew), or Intimidate (to press-gang new crew).
Each such check takes 1 full day, and a successful check results in 1d4+2 new crew members for the PCs’ ship.