A lot of good advice from BullHughes.
Also worth repeating the fact, that fuel mismanagement is the major culprit behind ditchings. Engine or structural failure is apparently less frequent.
In other words:
1. Carry a life raft & PLB (A/C ELT won't work underwater)
2. Only fly in good weather (duh)
3. Don't run out of fuel
...and your chances of making an ocean crossing should be perfectly acceptable.
I recently did a 3 hr open ocean crossing in a Diamond DA40 (Kuching to Singapore), and felt comfortable with our preparations.
Ocean crossings in the North Atlantic in the winter is a totally different ballgame of course, due to the spectre of hypothermia.
I'd add 3 additional points:
- Ditch without flaps extended. I read somewhere that the airplane is more prone to submerge (fly "into" the water) with flaps extended.
- Try to maintain control of both wings & keep them level even after the first bounce on the water, in order to avoid dangerous cartwheeling or submerging a wing.
- Start your ocean crossing early in the day. In the event of ditching it's much harder for SAR to spot you in the ocean at night. (don't count on help being there for at least a couple of hours)