We have the http://elderscrolls.wikia.com/wiki/Sload and their Semi Submerged continent of http://elderscrolls.wikia.com/wiki/Thras.
I doubt they can swim very well due to already being what would be considered highly physically disabled in real life. They can't grip anything by any means of the term. What they "grip" has to be absorbed to an extent before they can be able to hold anything. This probably takes a few days at worst. Let's not forget the fact that most of their heroes were very much too busy thinking and being cautious on "adventures".
Sload tend to be very much into necromancy, and are worse about it than any Altmer. I could see an off-shoot race of them that is more like those aquatic frog-like creatures from Shivering Iles, though. The ones that would almost always have pearls as loot, that is.