Dive 13 was conducted on a potential mud volcano site, dubbed Twin Peaks. Remotely operated vehicle Deep Discoverer (D2) landed on a nearly featureless sedimented bottom made of very small, pale-brown particles at a depth of 4,829 meters. At the start of the dive, we saw slabby exposures of rock a few centimeters to tens of centimeters above the sediment that were aligned in linear rows parallel to one another. The rocks were mantled with a black (likely manganese-oxide) coating, but at the base of some of the slabs there was an exposure of a pale-tan to yellow-orange surface with a rough, rubbly texture. The seafloor throughout most of the dive remained thickly sedimented. Based on the prevalence of the small outcroppings of sedimentary rocks throughout the dive, it is unlikely that this site is, as we had hoped, a serpentinite mud volcano. Rather, it appears to be a fault block of forearc sedimentary sequences. Fauna observed during the dive included swimming sea cucumbers, carnivorous sponges, acorn worms, several long-legged isopods, hermit crabs with commensal anemones, pregnant mysid shrimp, many stalked sponges, several deep-sea lizard fish (Bathysaurus cf molis), and a shrimp with unique adaptations that was unknown to our science team.