I'd say possible. Not sure I'd go with likely.
I see three friends sitting on the edge of the river, having a few drinks and recalling the good old days when he was the toast of the town. Then under the influence of alcohol and melancholy they cook up a plan to regain the fame and glory and it goes horribly wrong.
I'm not saying that's what happened, but another possible scenario...
The first time sounds legit, but lets put it this way. If he rescues another friend or turns up drowned in a couple of months, I'll be very suspicious.