OK so the video explains it - it wasn't the pilots' aircraft, he was renting it from Moore Air
http://www.mooreair.com/TheClub.html so he didn't care re salt water as he just wanted the safest way out which was in his mind was to put the aircraft in the lagoon.
Faced with an emergency this mindset may be a good one to have (hey it's only a rental) but I think I still would have chosen sliding on the runway.
Hope the insurance at Moore Air covers everything.