Unfortunately, Provo is not a great destination for snorkeling. There are a few sites accessible from shore in Grace Bay (esp. Coral Gardens), but other than that, due to the reef structure, most of the sites are too far and too deep to snorkel (the top of the wall is at 40-60 ft).

Coral Gardens is good, but the reef is actually roped off, so you can only swim around the edges.

Check these threads on ScubaBoard:
http://www.scubaboard.com/forums/bah...norkeling.html
http://www.scubaboard.com/forums/gre...er-diving.html

Can't tell you about snorkel operators, unfortunately, as we were diving (which was spectacular), but there may be more info on ScubaBoard.