Dive 15 took place at Mozart Seamount. This dive was chosen as a comparison to yesterday’s dive at Liszt Seamount, to contrast geomorphology and geological environments of seamounts formed via hotspot volcanism with different proximities to the Murray Fracture Zone. Remotely operated vehicle (ROV) Deep Discoverer (D2) arrived on bottom at a depth 3,853 meters (2.39 miles) on a talus slope with a single stalked sponge in view. D2 soon encountered a pillow flow front consisting of two or three thin layers, which was a stark contrast to the flat plain of consolidated pebbles D2 has started the dive on. Shortly afterwards, the slope steepened, thick manganese-crusting was evident, and we encountered our first coral of the dive, a Pleurogorgia sp. Further up slope was a low relief sheet flow and talus with a few sponges, sea stars, anemones, and corals. There were various kinds of stalked glass sponges spotted throughout the dive such as Caulophacus sp., Saccocalyx sp., and Hyalostylus sp. The geology highlight of the day was when contact was made with a field of nearly spherical intact “pillow balls” at 3,765 meters (2.34 miles), that seemingly rolled downslope intact. However, little evidence of slide activity was observed on the slope. The overhead ROV Seirios view showed a distinct contact between the “pillow balls” and a featureless slope which was very puzzling. Four coral specimens were collected including a Bathypathes sp. black coral, Anthomastus sp. mushroom coral, Primnoidae coral, and Keratoisidinae D clade bamboo coral. Four geological specimens were collected as well, two with our biological collections. All of these specimens will be great assets to understanding the biological communities at this depth and the geology of the Musicians Seamounts!