Through Carnival Cruiseline, we got to swim and touch stingrays through Emerald Eyes (Company? Boat?). All I know is that they were amazing!! The crew was there for YOU (and of course for the stingrays). They took the time to introduce themselves, the days agenda, the rules of engagement with the stingrays, and were always in the water with you in case you needed assistance.
I'm not a strong swimmer, who am I kidding, I can't swim but I felt very comfortable with the crew being close to me in case I needed help. They provide snorkling equipment and it is cleaned. After the stringrays, they took us to the corral reef and got to snorkle some more.