I shot a boat crew once, killed gunner and I believe the driver. The second gunner did not changed to driver position, but jumped into water, swam around and after I fired at him (and missed) he swam back to the boat and mounted the driver seat (started engines).
Maybe he panicked and it was a nice twist, but a soldier would rather open fire with his gun/sidearm and hide in the boat than jumping into water, unless boat burns or is about to blow up.

That brings me to:
http://feedback.arma3.com/view.php?id=5346