When I was 17 I visited a crocodile farm and heard this from the tour guide. It's always stuck with me.
When a male crocodile decides it's time to get amorous with his chosen female, he slides beneath her and blows bubbles along her underside as foreplay. If she gets excited and accepts his advances, he slips a leg over her and leads her down to the murky depths of the river or dam, and crocodile sex ensues.
However, should she not like his advances and turn him down, he comes up beside her, raises his head above hers and smacks it down hard, rendering her unconscious. He then slips a leg over and drags her down to the murky depths for crocodile sex.
So, if you come back as a female croc, remember when he's horny, it's bubbles or a thumping headache.