It was with the release of morrowind where they actively made water more shallow, with rich making a comment about this effort during a promotional event, as they were aware of the frustrations.

This is why in every content release since you will notice you get dismounted a great deal less when traversing through streams and such. But the original temriel lands remain untouched, and I can’t see them going back and re-designing those areas.

Guar should be able to swim as they have gills. Dwarven constructs should probably stay out of water, as well as storm and flame atronachs.