We spent a morning diving with Dive Rarotonga. From start to finish the operation worked like clock-work. Our guide was excellent - ensuring we saw as much of the sealife as each site had to offer (including the resident "pet fish" which tagged along at each site. Very safety-conscious as well - with a super-experienced/qualified skipper on board while we dived.
Overall, 2 awesome dives and back by lunchtime - ideal.