Hi, I might be able to help a little with the water. Its easier if I show you on your own piece of art what I'm talking about so I hope you don't mind if I drew over the top of it..
First, because of the perspective your longboats are at, there would *likely* be a horizon line behind them at some point, which I added. The big waves became the mid-ground, they show you how wild the ocean is. Because the swells you made were so large, and you implied a lot of big splashing, that should carry over into the rest of the water. Adding some whitecaps makes it look windy, stormy, wild. Toward the horizon the waves are almost indiscernible, but they should get larger and more pronounced as they get closer. Where the boats are breaking the waves, the water breaks at the prow, spraying up, and back. Just adding some lines that show motion helps with that.
Hope this helps, and hope you don't mind me drawing over the top of your image. D:
Emily