Who's to know if you could have saved him? You say he was a spiritual guy then who's to say it was not his time to go?

But there is a lesson you can learn from this. Live each day to the fullest and don't take things for-granted. You just never know when it's your time. Also you say he died from a heart attack what could you have done? Nothing. But if you want to do something positive make sure that the people you love and care about know how to swim. Do something in honor of him. But I can tell you he would not like you feeling responsible.

Take one day at a time.