I went snorkeling with a guide and my family just down from shark ray alley. It was chest deep. You could stand up any time you wnated, and I have to say, I saw cool stuff there that I never saw in the deeper places. Ask a guide to take you to a shallow places. There's loads of them and they will be happy to do it. If you're insistant on the rays, they could provide you with a life jacket or floatation device. They're wonderful about stuff like that. JUST ASK!
Debbie