I guess the biggest worry besides water-borne diseases would be the chlonination or chemicals used to keep the water free from those diseases. Depending on how his skin is. I honestly didn't think too much about it... Matilda was in a pool from week 8 I think, mid winter LOL, we always had a shower straight afterwards & a massage after with moisturiser... but she started swimming lessons at 4 months. She loves the water now and begs to go swimming. We haven't done swimming lessons in ages so we have to start up again soon.