You can tell from all the great reviews, just an excellent operation. If going to snorkel the Great Barrier Reef is a bucket-list item, and you may only go once in your life, then do yourself a favour and spend the extra 200 or 300 bucks and go with these guys, rather than the 100-300 passenger big boats out of Port Douglas or Cairns. The small group is great. The crew is very friendly, fun, informative and super helpful - personal attention to how the gear fits, answering questions and making sure everyone gets the most that they can out of it. I was a little skeptical of a "guided" snorkel in open water, but it worked! Each guide had a group of only 6 in the water, and these guys were educated so knew what they were talking about. Also did a pre-snorkel presentation onboard while we were en route, and had guide books for all to flip through. On board coffee, pastries, lunch were all really good. Had an excellent time, and the reefs we visited were the best i've seen on the GBR, in beautiful condition.
Really can't say enough about this group - a class operation, and well worth the extra you will spend. If you're at all serious about good snorkeling and learning something, go ABC.