NOAA Ship Okeanos Explorer had a great first remotely operated vehicle (ROV) dive today to kick off the 2014 Gulf of Mexico Expedition. ROV Deep Discoverer (D2) was launched to a depth of 962 meters at site GB648, now known to be a site of active hydrocarbon seepage. Shortly after reaching the bottom, D2 came across a potential extinct mud volcano. This carbonate structure was covered by encrusting sponges and bacterial mats and surrounded by dead mussel shells. As the dive proceeded, we came across several carbonate structures with apparent hydrocarbon seepage. Most notable was what our science team called the “Amphitheater of Chemosynthetic Life” – a large carbonate ledge covered in chemosynthetic mussels with methane hydrate underneath. Mussels were growing on top of the ledge, under the ledge, and upside down on the “roof” of the feature. Other fauna in the area included ice worms, sea urchins, fish, crabs, and starfish. Small white gastropods (snails) were common close to active seep sites, likely feeding on the chemosynthetic bacteria. Many bacterial mats were seen in a range of colors (white, orange, and black) and always associated with seeps. Corals were rare and low in diversity throughout the area. Other dive highlights included a hydrate tube that had a stream of both oil and gas bubbles, rapid hydrate formation around methane gas bubbles (similar to a rind of ice), and a large structure covered in mussels in the proximity of several bubble streams. During this dive, D2 also successfully tested two new pieces of equipment—a temperature probe and downward-looking mosaicking camera.