Oh heck ya! I was tubing a pond in North Central Ok a couple of years ago and had a big water snake make a beeline for me. I beat the water like you said and it disappeared, only to surface and climb on my tube with me. Bugger was almost 4' long, and was a handful to hold until getting to the bank to release it.
A year or so later, talked to some folks that tournament fish from float tubes and told of my experience. He said the solution is not to slap the water, but to use the tip of the rod gently to re-direct the snake until it moves on. Slapping the water with the rod puts it into panic mode, making it want to get out of the water, and the tube fisherman is the closest way to do that.