Hi,
Aimee the first poster said the rules were 6. I just checked Dolphin Discovery website and they say 8. I booked directly with Dolphin Discovery in Cozumel. When we went, last minute they added two little girls, who one of which could have been 8, but the other, no way. The parents did not go in with them, they stood up on the landing taking pictures. You might want to just email them and see what they say. If your DD is a strong swimmer, they might bend a bit. Good Luck, it's worth it!
Robin ºOº