There are three parts to this tour: snorkling, an island walking tour, and a glass bottom boat ride. Try to get in the water during the lowest tide available that day. At higher tides you will spend a lot of effort trying not to hold your position, which distracts from watching the fish. At low tide, the reef pops above the surface and the strong current pretty much disappears. They assign you to groups on boarding, so I am not sure what it would take to change to a lower tide group. Also, wear plenty of sunscreen, reapply frequently the sun is amazingly intense and TAKE SEASICK MEDS. It's a rough ride out and back without them.