It's highly highly risky, and pretty likely that you'll survive. I mean, you could certainly do things to increase the chance of survival, but i wouldn't count on it.
I've survived drowning when attempting to rescue another drowning person (without training), and the primal fear of even being near moving water is so strong for me now that even if I wanted to CTB via drowning, I couldn't will myself to. I used to love swimming, no matter where it was, I was ready to jump in almost any water, but now it's hard to get in a pool. so yeah, if you fuck up, chances are that your body won't let you try again that way.