Turning and looking around speeds when you are underwater are the same as when you're on land, which is unrealistic, and shouldn't happen, no matter what the mouse sensitivity settings are. A good/more realistic proposal, should be to lower the sensitivity a bit and/or force a high amount of smoothing.
- Legacy ID
- Swimming and Diving
This issue is somehow related to this one: http://feedback.arma3.com/view.php?id=912
Looking around when you're under water is actually not a problem, and you can do it as fast as out of the water.
On the other hand, one could argue that you can't turn around with two hands on the rifle (you'll usually have to use your left hand to change your orientation).