Just a thought. The last RAF crash we had in the sea was a Tornado at Holbeach range a few weeks back (OK, it wasn't quite in the sea as they ended up on the mud flats). Considering that everyone knew the location of the aircrew, there were more PLBs going off than I've had hot dinners and there were three helicopters dispatched to the scene (one of which was actually rotors turning at the time), you may be interested to note that Peter the Pilot and his WSO bag carrier were left pondering life, the universe and everything else for 45 minutes before the were joined by the ever heroic helicopter crews.
IMHO that, unless you are extremely lucky, you should plan on being in the water for at least an hour and probably two.