This is the highlight for me, although almost everything was amazing. They pass the reef in a wall of sharks that fills your field of view: I have a full-frame, uber-wide-angle lens and it still does not do reality justice. And swimming out into the school is truly one of the most special moments of my life: they open out around you and you end up in a bubble completely surrounded by these beautiful animals.
Many people do not believe that this is safe. It is: they have no interest in us (and in fact do not like the sound of bubbles). Also, they are not in this location to eat. It is a cleaning station, where small fish pick off parasites etc from the sharks. Even eagle rays (which hammerheads do like to eat) are not concerned by the schooling sharks here.