Most of the divers on this trip focused on the Manta Rays, both open circuit and closed seemed to enjoy the Manta Rays. I think the open circuit is just too loud for getting close to the Hammers, and hanging between 80 and 85 feet at thermocline for over an hour really is only realistic on a rebreather. Another great diver we dived with regularly was Michael Prange, also an Inspiration rebreather diver, who also got some killer video footage of Hammerheads.