I agree with the PP, I don't think it's probably necessary to talk about autism to explain this one - kids jumping on each other at the pool is pretty typical of NT kids too... I just say that DS's brain works differently, and that works for my DD, but that doesn't help when he bites her or tries a WWF takedown! Those are "normal" two year old behaviors that we talk about separately from his autism. (It's tricky when your two year old outweighs your 5 year old, sigh...).
Pick battles big enough to matter, small enough to win. ~Jonathan Kozel