Manta rays feed in the pass swimming up and down for hours. The best time to go is a couple of hours before high tide. There is a bit of a current but not so strong that you can't swim against it fairly easily. Better still, just stay in the one spot and let the rays glide past. Avoid damage to coral by having someone stay with the dinghy. There is also a lovely big gorgonian coral fan in the pass and usually a cloud of fusiliers and other fish life hanging off the western end of the pass.