The eastern pass of Rangiroa is the place to watch spinner dolphins. Each morning on the incoming tide, a resident pod of several dozen dolphins rides the current through the channel, spinning and leaping in the bow wave of the tidal flow. You can watch from the bank for free; dive operators take divers in to swim alongside them.
Tiputa Pass is also excellent for sharks — hammerheads are seen here more often than at Avatoru Pass — and for large pelagics following the current in from the open ocean. The pass lies on the far side of the atoll from Avatoru village; water taxis cross regularly from the Avatoru waterfront (about 1000 CFP).