I found jumping off the back of that motor launch into the big rooster tail of aerated sea water far more daunting than the HUET itself.
The first time our OCU course did the sea survival training off Mountbatten, it turned into a real rescue because the swell was stronger than the staff anticipated and we began getting washed onto the rocks on the seaward side of the breakwater. The Whirlwind got called away part way through the winching exercise but had to come back to rescue us!