My daughter will be two months short of age 6 (the cutoff for the dolphin swim) in May when we are considering visiting DC. I just called DC and the very helpful woman on the phone said they don't really require any proof of age unless the child obviously appears to be under 6 years of age. Well my daughter is a little on the small side but will be 5 years and 10 months and should pass by. Has anyone run into a problem before? We probably would not go to DC if I think she would not get admitted fro the dolphin swim.