This probably sounds fairly ridiculous- I know, but in short I've been developing a sort of future earth. It's not extraordinarily accurate, but I've been trying to at least keep the obvious in check. As far as I've seen, there's really no long legged semi aquatic animals, and it's easy to see why.
Still, is there any way one could develop in such way? Something like a cheetah in the process of adapting to adapt to a new environment, maybe in the very early stages? I've been using cheetahs as a reference, as the made up creature is built (somewhat) similarly. I considered if it could be initially an animal built for chasing down its prey, but another more successful species made that life style too hard for our "cheetah". This sent it to another niche, fishing, which its specialized form isn't built for exactly, but is changing rather quickly to adapt to.
This was the best I could come up with, but I honestly found it much too complicated to be plausible. Could something like this potentially happen, or is there an even more reasonable explanation? My end goal is to keep the creature relatively the same, with its long legs, longish muzzle, and small eyes and ears, but to also keep it along rivers.