@eoe,
No under age limit in diving.
Britain, for instance, has a quite capable 14 year old.
In fact, the tiny 16 year old Chinese divers make me think that either the Chinese are too clever and also changed their ages or that they somehow mess with their bodies through training (and something else...), 'cause an underweight diver makes cleaner entrances (all the rest of the dive being equal, splashes less water).