The only drown proofing I can think of is what the Navy Seals do in BUDs. They tie their hands behind their back and their legs together and then pop up for air when they need it. It's a lot harder for those guys because their body fat percentage is microscopic so they sink like rocks. They would probably have to give me a couple pounds of lead to sink properly...

https://www.youtube.com/watch?v=1Pe3L5OcAEg