Hmm, the entire concept of Aquatics brings into question Stellaris' planet class system, which is based around a planet being considered homogenous for habitability. It would be very strange to see Aquatics with Desert Preference, but then that super imbalances things towards the "wet" category if Aquatics just always have a preference in it. My hope would be that we're finally getting planets divided up into habitability type zones, so Earth would be composed of a tropical part, a temparate part (ideal for humans), a desert part, a savannah part, an arid part, a tundra part, an alpine part, an arctic part, and a few types of ocean parts.
I suspect instead we'll just get planets divided into land and sea, but that would at least be an improvement if no species had perfect habitability in both, meaning that finally, there'd be a reason to fill out certain planets (like Gaias, but also obviously Ocean, Continental, and Arctic at least) with multiple species to maximize them.
