We went with Hang Loose boat tours snorkeling to Captain Cook Bay and also whale watching. To be perfectly clear!!!! - Hang Loose boat tours, Captain Simon and crew, were fantastic on both tours. Entertaining, knowledgeable, great boats, etc. - made both tours super fun and well worth it. The boat has 2 decks so you could choose whether to be on the upper or lower deck. The catamaran design makes it more stable. The lunch they prepared on the snorkeling trip was excellent - yummy sandwiches, great fruit, snacks. On both trips we got information on the island as we traveled along and he stopped several places for us to take pictures. I would definitely, definitely recommend Hang Loose boat tours and we would go with this company without hesitation.
Now to the snorkeling review - the only reason this review isn't a 5 star is solely on the quality of the snorkeling, which doesn't reflect obviously on Hang Loose. We are long time scuba divers/snorkelers and went diving throughout the Caribbean and also Cozumel and Honduras. The reefs of Hawaii can't compare to the Caribbean - just a simple matter of lava reefs versus coral. Captain Cook Bay is "the place" according to everyone to go snorkeling on the Big Island (we have no experience with the other islands) but for people who have snorkeled other places, Captain Cook bay was very disappointing. Again, compared to the Caribbean - not a lot of fish, green/blue lava reefs, probably 15 boats, a hundred people in the water with pool noodles. The snorkeling on the Big Island is a 1 star at best if you are familiar with other parts of the world, in our opinion. But definitely go on the charter for fun - just don't expect much with the reefs.