There are several KB Beach, Foghorn, and Gull sounds also.
There are many textures that are best set to minimum scale when painting.
There are many fish, and whale static assets by Whecsailor.
The shallow water could be a slighly darker shade, with ever increasing darker textures on the sea floor color, that can be painted a dark greenish/grayish/brown, and the water level/sea floor depth needs not to be really deep.
You could drive, exploring the sea floor in a submarine, using BNSF50 Invisatrack.