We have the same trouble here and I'm not getting very far with it either. He tries to drink bathwater out of any container, I say 'yuck yuck, not a drink' and move it away. He does it again, I move it / pour it away. I don't let him do it, but that doesn't stop him trying all the time.
He also shoves his face in the water and gulps - foam and all. He's done it a few times and not enjoyed the experience, but it hasn't put him off. He keeps doing it and I don't always get to stop him intime.
Worst thing for us is that he does this during his entire swimming lesson. So he's constantly putting his face in the water to gulp the water. The teacher keeps warning me that he'll get a bad tummy from this. I say no, stop him, but not sure what else I can do.
Babes.
At least it's less grubby that pulling his widger off constantly. He's already started putting his hand down his trousers to see if he can wangle it into his nappy. Not a great habit when I'm changing his nappy... so could be worse