You are too funny! I was going to say ask the pedi, but I may be pressing my luck!! :) Just kidding!
Yes, the swim diapers are a must, regular diapers will swell to a size that would astonish anyone! I think it would be possible to cut the circulation off to the lower body in those things.
Just remember to put the sunscreen on at least 30 minutes before going to the pool and reapply frequently. (Don't forget the ears.) And be sure to bathe him after to get all the chlorine and sunscreen off. That can be rough on his baby skin.
My dd only tolerated a few minutes at a time in the pool, though she loved the water, she wanted in and out. ???
I used a sun virsor and sunglasses to protect her eyes. The swim hats seemed a little too hot. I also got a little tube of lip protection for babies, because I didn't want her lips to burn and that sunscreen tastes AWFUL!
He may not appreciate going under at this age, but some moms start teaching them to go under and swim by blowing on their faces and going under with them. Just beware of him gulping too much water-that can cause serious problems. If he isn't gulping the water, be sure to keep him hydrated, sometimes we forget that around the pool.
I guess that is all I have to offer, except to wish you a ton of fun! Let us know how he does! :)