Your ability to operate a boat. Everything from paddling a single manned craft to commanding large navy's.
0: You've probably been in a boat before.
1: Basic understanding of what to do in a boat.
2: A valuable member of the crew!
3: You know how to weather a tough storm and keep the ship upright.
4: Your comfort on a ship is astounding, this is second nature to you now.
5: Aeran Admiral material. You know the ins and outs of any ship at sea.
6: Aereth has been wondering how you made it from Lorandor to Aarandor with out sinking, and only you know the answer.