opened up a generator to get me started with an idea and it spat out sea squirrel (well, ocean squirrel) xD
base animal is a squirrel mixed with maybe an eel, catfish, and maybe a bit of penguin.
mostly aquatic, semi-terrestrial:
-it can come on land and waddle about, but it is not at all fast or agile. lightning fast swim speed
-can use its face whiskers to grab maybe? used in water to anchor self while it eats
-comes on land to rear it's young, usually in small burrows around tree roots
best parts of a squirrel and a fish:
-breathes air, but is efficient at holding it's breath
-its fins are actually just really stiff fur that hold together with oil from the creature
-ears are mostly for mating display, and are not so much actual ears but fur tufts resembling them, so these are variable in size and shape
-prefers to eat vegetation or insects, but will scavenge meat when available. borderline omnivorous i suppose
-depending on the type, the tail would have horizontal or vertical fur, moving either up/down or left/right accordingly
tropical climate, fresh or salt water:
-no color or pattern limit since it's fishy, and they're all sorts of neat colors
-size can vary depending on how big the body of water they're in is. probably caps out around a pomeranian size body. the tail would be as long as they're able to maintain, with the part past the tail-tip just being fur
uhhhmm i guess that's it? xD sea-squirrels. the name would probably change... squirreels? searrels? i don't know

