The purpose of Dive 9 was to explore the deep-sea coral and sponge community on an unexplored ridge feature off the southwest coast of Puerto Rico. The dive started on a relatively sharp, sedimented slope and then transitioned into a steep ridge with occasional jagged pinnacles. At least nine different species of deep-sea corals were documented at the site, including black corals, scleractinian corals, pink corals, bamboo corals, and chrysogorgiids. Particularly noteworthy was one very large colony of the precious coral Corallium niobe, as well as several colonies of the gorgonian octocoral Iridogorgia magnispiralis that were between 1-2 meters height. Throughout the dive, we noticed thick stumps covered with ferromanganese crusts, which were presumably the remnants of old coral colonies.

Sponge diversity was quite low at this site and consisted mostly of encrusting or stalked species. Sea cucumbers were common in soft sediment patches along the seafloor. Other echinoderms seen during the dive included five different species of sea stars, one crinoid, and one brittle star. Additionally, we recorded three different species of fish, including two tripod fish and one cusk eel, all of which were seen on soft bottom habitats. We also observed a fair amount of organic and anthropogenic (human-made) debris during the dive, including tree branches, seagrass, bottles, and plastic.