I'm not particularly digging the sea that way. To me it draws the eye too much, and it gives a really odd sense about your ocean, with very deep sections dotted across it semi-randomly, some occurring right offshore.

My suggestion would be to borrow a technique RobA uses in the artistic regional map. Take a basic mask of your landmasses, blur it a lot, then map your deep sea and shallow sea colors to it on a gradient. You get shallow seas near landmasses, and progressively deeper seas farther out.