A cerianthid with long, slender tentacles against a rocky underwater background.
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Cerianthid
A large darkly-colored cerianthid observed during Dive 05 of the Papahānaumokuākea ROV and Mapping expedition at 1,243 meters (4,078 feet) depth. This family is known for dwelling in tubes, although this specimen seems to lack a tube.
Credit

NOAA Ocean Exploration, 2025 Beyond the Blue