If you're a casual holiday-diver, or have a non-diving partner, then a Cook Islands scuba diving holiday may be just right for you. However, advanced scuba diving enthusiasts will probably find the diving variety to be too limited and should investigate either Fiji, Tahiti or Vanuatu for a scuba diving holiday.
The beauty of scuba diving on Rarotonga is that it is a small but mountainous island so there is always favourable diving conditions. If the wind is blowing from the south-east, which it usually does, then scuba divers head over to the dive sites along the north and west coast, but when the stronger northerly winds blow in, there's sheltered diving along the south coast reef. It doesn't matter at all which Rarotonga accommodation you stay at as all four scuba diving operators on Rarotonga offer complimentary pick-up and you're never more than 30-minutes boat ride from the dive sites.
What you will see is walls and steep drop-offs, boomies and Gregorian fans and mostly hard corals, although there are areas of soft coral in places. Pelagic fish are a highlight, with deep sea surrounding Rarotonga, and perhaps a chance encounter with a humpback whale when they pass the coast from May to October.
Aitutaki has more advanced dive sites with some good drift dives along the fringing reefs of the outer lagoon and these can be anywhere from 20 minutes to an hour by boat from Arutanga Harbour where the two scuba diving operators are based, again offering complimentary pick-up from all Aitutaki accommodation around the main island.