I did the full sea survival course some years ago before working in the Artic for a short period. While I still recommend doing it as you will learn a lot the over-riding impression I left with was basically an appreciation of just how stuffed you are and difficult it would be to be one of the folk that managed to get off the ship. get to a liferaft, get in and finally survive until picked up.
I suppose this is not neccessarily a bad thing to stop overconfidence