First, my review of Hang Loose, a 5 star experience. Captain Tim and his mates were first class and we always felt safe and cared for. The munchies and drinks were tops and the croissant sandwiches for lunch were fresh and tasty, including a good vegetarian option. The boat was fast and comfortable, with ample shade; you don't even need a hat! Though you can choose to go up front or on top for all the wind and sun. All equipment is supplied, and they make special efforts to help newbies. I don't think they advertise it, but there IS a marine head. Everything was on time and we enjoyed the ride back where Tim spent time checking out some interesting coastal areas. He also stopped so we could watch a big Tiger Shark in the harbor and he ran along with some Dolphins. So this was much more than just a snorkel tour. But we spent plenty of time at the snorkeling site. If we go back for a different tour, like the Manta Ray tour, we'd definitely take Hang Loose. Why: comfort, shade, speed, service, and food.
Second, a review of the snorkeling, which was good not great. I guess if you're only going to do ONE snorkel while you're on the island, AND you don't have equipment, AND you enjoy a nice boat ride, this is a good choice. But you'll be with too many other snorkelers, and even some jerks with kayaks were crowded into what turned out to be a small area. I got kicked 5 or 6 times and run over by a kayaker. Also, the water gets a little churned up. The clearest water when we were there in the AM was right in front of the monument. You will absolutely see fish, and you will see some coral. But frankly, I saw as many fish at 2-step, and nearly as many at A-bay, 69, and Kahaluu, all of which are free.