Jellyfish
Although most jellyfish live well off the ocean floor and form part of the plankton, a few species are closely associated with the bottom for much of their lives and can be considered benthic. The upside-down jellyfish in the genus "Cassiopea" typically lie on the bottom of shallow lagoons where they sometimes pulsate gently with their umbrella top facing down. The tiny creeping jellyfish "Staurocladia" and "Eleutheria" cannot swim, and "walk" around on seaweed fronds or rocky bottoms on their tentacles. Most hydromedusae and scyphomedusae that live in coastal habitats find themselves on the bottom periodically, where they may stop swimming for a while, and certain box jellyfish species also rest on the sea bed in shallow water. Even some deep-sea species of hydromedusae and scyphomedusae are usually collected on or near the bottom. All of the stauromedusae are found attached to either seaweed or rocky or other firm material on the bottom.
Crossota millsae
"Crossota millsae" was first described from the Pacific Ocean off Hawaii and California. It was subsequently found in the Arctic Ocean and in Guayanilla Canyon off Puerto Rico. NOAA researchers who filmed this species in 2018 near Puerto Rico called it a "psychedelic" jellyfish. It lives below 1 km depth in all four regions. Its highest abundance is found at 2500 m off California and 1250 m off Hawaii. In the Arctic Ocean, it has been observed sitting on the seafloor.