Exactly what can a younger diver do if they are ready to go beyond the PADI Seal Team?

The great news is that they can do pretty much every course, just with a few restrictions.

We will not accept students for any course that involves diving in one of the training lakes until they are 12 years of age. Once they turn 12 they can take part in any of entry level, and most of our higher courses.

After certification there will be a few restrictions.
Aged 10-11 are limited to a maximum depth of 12 metres and they must be accompanied by a parent (certified diver) or a professional diver.

Aged 12-14 are limited to a maximum depth of 21 metres (18m for openwater course) and must be accompanied by a certified adult.

Age 15 and above there are no special restrictions other than for a few of the specialty courses, age limits are stated on each courses page.