We just sailed with Captain Bryan's in Grand Cayman last week and had an absolutely amazing time. The crew is awesome! The boat is very cool (catamaran). Even though the waves were a little high it was such a great experience seeing and touching the stingrays. I have snorkeled quite a bit in Hawaii so I have experience but my parents were with me and they had never snorkeled and thought it was fun!
Captain Bryan's is $34 for 2.5 hours. 35 minute ride to Stingray City and back but plenty of time to snorkel.