We first saw this on petapixel – a diver was swimming with a bunch of Manta Ray's and filming them with a Canon EOS 5D Mark II (reviews) when one of the rays decided to take his whole rig for a little adventure!
From the youtube description:
What began as another exhilarating manta ray night dive off Kailua-Kona, Hawaii on an August evening in 2010, quickly turned into the theft of the century. Cameraman Travis Matteson was capturing footage for the scuba diving travel television show “Into the Drink” aboard the Kona Aggressor II. Suddenly, one of the manta's giant wings hooked his light system, and darted off with the nearly $10,000 worth of photo gear. Underwater videographer Johnny Reidt caught the entire theft on camera, and the manta, carrying the stolen photo rig, captured some amazing footage of the nighttime reef. Remarkably, the camera rig was found completely intact after an eight-minute run by the manta, just yards from the dive boat. Case closed.
(Photo credit: snap from the video)