Blue Hole snorkeling was fun for us. It is after all an iconic ocean image that made the world aware of Belize, and it is sort of exciting to say we have been there.
But on the other hand, if you had read on this page our story of what hell it was to get out to the Blue Hole, it was definitely not worth it.
Also, the Blue Hole is actually pretty unimpressive at water level. Our boat stopped, and our guide told us we were there. Yep, it pretty much looks like any other spot on the water. You can see a nice big ring of coral, with a slightly darker center, but it is much more impressive from the air.
Once in the water you snorkel around the inside of the reef ring, and below you the sea floor drops off nearly vertically into the depths, with very little sea life on the walls. Near the surface we saw some beautiful corals, fans, and sponges all around the rim. It was probably the healthiest reef we had seen in Belize, but it was not that much better than anything we could see closer to the barrier reef, a mile from our hotel (instead of 50 miles across open ocean).
Unfortunately there were very few fish at the Blue Hole. Deep down in the depths we could see some bigger fish, barracuda, some big groupers, and a handful of big sharks. But around the reef, there were very few tropical fish. So for a snorkeler, the Blue Hole is kind of a ho-hum experience.
One plus was that the underwater visibility was surprisingly good considering how much wind and waves were hitting the reef on the ocean side.
One very negative factor to Blue Hole snorkeling is that the guide boats leak gasoline which coats the surface of the entire area, and when you snorkel you end up breathing and tasting the fumes the entire time. It was very unpleasant, and is probably an environmental nightmare. It could also explain why there were so few fish.
So all and all, we would say skip it. Save your bucks and butts, and explore the spots along the barrier reef.