Luckily... the layout seems functional, so you will save lots by not having to more any plumbing. I would replace the flooring, countertop,hardware, plumbing fixtures, enamel the cabinetry and re tile the wall. I would put together a budget and assess what is most important to you of those items.

Just because you live on the water, you don't have to go putting shells in your bathroom. If you want to introduce the "ocean" feeling, I would select blues, grays and whites as the color scheme. This way you still get the "ocean" vibe but it doesn't look "themed." I like the idea of the round glass tiles that have the "bubble" look otherwise a clean subway tile is classic and affordable. You could even choose a color, depending on which style you are going for.

Best of luck!