It would be smart to have protection when wandering near the coasts of Morrowind and Hammerfell, because TR recently got a hold of these fearsome critters.
First up is the Hammerfell Moorcrab. This crab is bigger than the Cyrodiil variety, and has a dark, patterned shell. Made by Aeven, it will be included in the next merge of OoT.
Next up we have the Morrowind Seacrab. This crab is just one step in the project to re-do TR Morrowind's creatures, many of which looked wrong or did not work correctly. dirnae is undertaking this massive feat. The Seacrab and the Muskfly are currently in production, while the Esurio Viridis, a giant man-eating Venus Flytrap, has already been completed.
(I've removed the sea crab screenshot since the link was outdated)