"Ah!" he didnt think she was going to do it, he put it out there but he figured for sure that it was just going to end up her swimming away.  But now he was underwater with his older sister holdind on to his penis.  He struggled to get the advantage but all he ended up doing was wiggling around.  She had his dick hard around the base and it didn't feel bad at all.  Fine, he though if she is going to play this way.  He reach around her to her plump ass and gripped it tightly.  "How is grabbing my dick teaching me a lesson?" he asked at he got to the surface.