In reply to johncoxmysteriously:
As you say, if tied to a partner they can haul you out, losing your harness is going to make that more difficult.
I agree about the knife, if I was in a position that being in the water and having my harness on was increasing my chances of drowning then with a modern quick-lock buckle harness it's going to be a lot quicker to reach to your waist, loosen the buckle and let the harness fall off you than fiddle around trying to find your safety knife on a gear loop, unclip it battle with getting it between your body and waist loop and then find it takes a couple of goes to cut the harness material... all while drowning.
Having said that, avoiding going for an unplanned swim by looking at the weather and swell forecasts, tying in at the base of the cliff and short roping any 'bad steps' if not confident to do so without is by far the easier, drier and less deathy option!