This depends on the density of the gasses for some like helium which is lighter than air, floats to the top of the atmosphere and heavier gasses like carbon dioxide stays on the bottom of the...
Any animals in the coral reefs (eels, star fish, sharks, seaslugs, crustaceans, etc), dolphins, sea turtles, plankton. Think of the "neritic zone" as coastal waters (extending from the low tide mark...