My son was 8 when he did it. The waves were high and all the other tour companies cancelled their trips to the sand bar except Capt. Marvins, which we were on. My husband just simply held onto my son around the waist and he got to experience everything. He's a good swimmer (always had our own pool), but the current was really strong and he was a little intimidated by the rays. They have life preserver belts that your son can wear too. A lot of the adults even wore them. It's an amazing experience so don't let his age hold you back! He'll remember it forever!
