Yeah, I'd love to see some kind of a merfolk or lizardmen faction but Darvin's right unfortunately.
Even if they ruined the concept of an aquatic race by making it equally good in water and on land other land based races couldn't properly get to them in their water habitat.
The first duty of every Starfleet officer is to the truth, whether it's scientific truth or historical truth or personal truth! It is the guiding principle on which Starfleet is based! *Jean-Luc Picard*