Whilst swimming or diving, any attempts to traverse over a submerged rock in shallow areas results in the character becoming stuck on top of the rock.
Any attempt to unset the character from the rock proves fruitless even though the player can turn and crouch etcetera whilst fixed in place.
Easily reproduced regardless of character type - be it civilian, diver, or just a swimming soldier.
Occurrence seems more likely with small to medium boulders just beneath the surface.
From my own personal experience (and bruising - LOL) shallow coastal rocks are typically covered in extremely slippery algae (moss) and I feel the addition of slippery surfaces on semi-submerged coastal rocks/shelves would only increase the realism and effect of the virtual environment in ArmA 3.