I like a lot of the screens, however the last one has an overabundance of shrubbery. I'm guessing the viney plants at the bottom are meant to represent seaweed etc, but its a bit too much with very little variation and covers up almost all the tile and possible terrain elevations making it extremely flat looking.
The green fog does a good job representing the underwater sea life, however underwater areas around that depth are a more turqouise/blue color and have quite a bit less undersea life.
The angle its taken at doesnt do a good job implying its underwater either, normally underwater screenshots show a significant background where the doodads and terrain fade into the fog showing the undersea terrain. Try avoiding any views similiar to the default angle to make it a much more interesting shot.
In short:
Bring the angle closer to the ground
Decrease the spammed viney plants

, and add a larger variety of aquatic greenery and animal life
Adjust the fog tinting to a more blue-ish color to more accurately portray the depth
Show more of the actual terrain (not doodads) to show and have more height and tile variation
Try adding larger coral/reef structures and ruins.
+Rep fa sho