It's been a while, Adam! Glad to see you're here and still pixellin'.
About your piece, everything looks lovely. Seeing from how detailed your mountains are, I think the sea tiles should receive the same treatment. I'm thinking the waves should go in the direction of the coast, but if you'll have more than just a coast on the east side, then you really need something more generic, perhaps using diagonals, kind of like:
...but you will make it much better, I'm sure.
I did round some corners in the coastline, and I'm not sure it's possible, but you could totally ignore those.
Perhaps the sea should be darker overall?