Theres a million options for Manta Ray tours - rest assured that this one with Hang Loose will give you exactly what everyone is telling you you should see.
Definitley bring a towlel and small bag for personal belongings while yoh are on the boat, as well as some cash to tip the wonderful, professional, and knowledgeable crew. Some warm clothing for the ride back will help make your experience great as well.
Bottom line is you get to see the harmless and friendly manta rays up close - VERY up close! Once in a lifetime experience.