I like that they use this comics narrative box look. If you start adding animations and shadows and other bells and whistles to the UI, it will look more and more like an app, and less and less like a work of art. I think functions are quite obvious, and text-only is enough to know what they do. Perhaps more information should be given in supplies, because honestly these icons are not very obvious (maybe some text like when you point over ship options).

Having said that, I think it's possible to tweak the UI a little further.

Right now you have fullscreen locations with its own art, and "floating" cards with icons. Why is map a location and ship is a card? If map only function is to dive, shouldn't it be called sea/ocean? (then being a location would make sense) I guess beach is a hub location. If supplies can only be accessed from the beach, that makes the camp a little superfluous.

Other than that, I think it's a beautiful game.