Via the BB Submitterator, Melanie says,

A camera crew for the show Into the Drink was filming Mantas off the coast of Kailua-Kona, Hawaii when one of the giant Pacific Manta Rays took a camera off one of the divers. After swimming around for a bit with the camera still rolling, the Manta dropped the rig off on the sea floor under their boat. Another diver filmed the camera equipment being taken by the Manta.