Swimming baby question

Amy • Met my hubby in 2011 we became great friends, started dating 10/14 and were married July 2015. Now we are a family of 3! 👶 Baby #2 on the way!
So my baby should be born july 20th if not sooner (he is growing 2 weeks ahead:) ) but i would like to get him in the pool as soon as possible. Swim diapers start for around 16 lbs. Whats something i can do for him when he is smaller.