Awesome experience, very friendly and professional crew. We even saw a pod of dolphins as we were finishing snorkeling; the crew took the time to take us farther out to see them up close.
I noticed while we were out snorkeling that a lot of the other snorkeling tours were wearing life jackets fitted around the chest and neck area. I can't say from experience that it would be harder to look underwater with one of these vests on, but I would assume that it would be because you need to be able to keep your head underwater.
Instead of vests, this tour used flotation belts which in my opinion seems like a much better option since it does not restrict you from keeping your head beneath the water.