Before I did a HUET course with careflight I thought I'd be OK if I had to ditch in water. Just get out, right? How wrong I was. After doing the theory and getting dunked a few times I was amazed at how disoriented I became under water. Removing the seatbelt too soon means floating up to the floor of the aircraft (you will most likely be upside down). Add to that darkness, cold, panic and water up the nose and you may start to get an idea of what you are up against.
The training provided is excellent and I am now confident that I am armed with skills that may one day see me through a sticky situation. Look up careflight here - http://www.careflightsafety.com.au/
If you EVER fly over water then do a HUET course.