K.M.
It may be more that the pool is intimidateing to him. I brought my son into a pool very young too and when we did that I put him in my HotSling for water play.
http://www.bellyelan.com/proddetail.php?prod=HSPoolPouch
I think it made him feel safter. Otherwise I will suggest you set up the play pen under an outdoor tent and allow the family outdoor fun the baby in the play pen with toys and the rest of the family in the pool.