Close-up of a blue sea anemone with extended tentacles underwater.
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Blue Tube Anemone
A blue tube anemone (a ceriantharian) observed while diving on an unnamed seamount in Papahānaumokuākea Marine National Monument at about 1,757 meters (5,764 feet) in depth during Dive 05 of the 2016 Hohonu Moana: Exploring Deep Waters off Hawaiʻi expedition.
Credit

NOAA Ocean Exploration, Hohonu Moana 2016