That's a great loss. I bet the son is probably blaming himself. For a son to loose a father that way is awful. It just goes to show you how quick it can happen and happen to anybody. How old was the son, was he real young? They say cold water is a real shock to the body. If it is prolonged it disrupts the normal thought processes and you loose control of your limbs so ordinary swimming becomes difficult. Trying to keep from panicking is probably the biggest fight.
Deck Rigging Gear
The Kayak Wing