I like the idea of a water/ice-based creature, because that balances with Humans (open terrain), Dwarves (mountains), Elves (forests) and Ingmarian (desert). I'm also okay with them going ten minutes underwater so long as they have difficulties not on flat land but more so on difficult land like slopes and up in trees. Webbed versions of human-feet, maybe? In water, they can swim well, yes, but I won't have their stamina wouldn't be too much different than that of a pro swimmer in human terms. In other words, while they are far more capable, they can't travel from continent to continent without the aid of a boat or something similar.
