BeeGee can swim, whether he likes it or not is another issue. The first time he was ever near a swimming pool, he just launched himself into the pool, and promptly sank like a stone. I dont think he realised it was deep. Of course someone fished him up really quick, in all the whole episode would only have taken two or three seconds so he was never in any danger. Since then, he has figured that he can swim
Maddy loves the beach, she like to play in the waves, although she's such a wee thing, I do worry about it getting too deep for her (our beach is pretty wild).
I wouldn't worry too much (especially if you have a jacket for him) I'm sure he will cope in the water.