I did the morning sail and snorkel tour. The boat was lovely and not crowded, and the crew and captain were friendly and efficient. It was enjoyable to see some of the coast from the sea and to hear some history, legend and anecdotes.
However the snorkeling at Captain Cook was disappointing. Similar to what I'd seen at Kahalu'u Beach in Kailua and much less good than at Two Step. Both of these are shore snorkeling sites easily reached independently. The other snorkel site "Ridges" wasn't any better, though much improved when I spotted an octopus and managed to follow it for several minutes. 🐙
The crew in the water (one on an SUP the other in the water, I had no contact with the one in the water as they were not identifiable!) were happy to answer questions I had, but there was minimal briefing given on what you were likely to see whilst in the water or on particular locations to look for within the sites. Other than don't go beyond X and Y or too far close to the shore....
So - if you're a confident independent snorkeller, I'd suggest investigating all the shore snorkeling sites you can find rather than spending money on a boat snorkeling trip. If you're not confident, this is a good tour but still costly