Mobility: yes. Especially the damned beard, it floats up into my face. It's also pretty heavy when waterlogged and I'm climbing back up the ladder.
Fish reactions: I think so. My zebra shark buddy isn't quite sure what to do about it. Only got a couple face bumps, instead of a bunch of them. The black tips are the ones to be concerned about... but they typically don't get within 5 feet of me unless unless one of them hits a fish and they all kind of frenzy. Most of the divers have had an experience with that. So no, they don't appear fazed by the santa suit.