A large solitary hydroid (Branchiocerianthus sp.)
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Large Hydroid
Among the notable biological sightings from the Beyond the Blue: Papahānaumokuākea ROV and Mapping expedition was a large solitary hydroid (Branchiocerianthus sp.) seen on an unnamed seamount. With a diameter well over 1 meter (3.3 feet), it was the largest hydroid ever seen by the shipboard science team. 
Credit

NOAA Ocean Exploration, 2025 Beyond the Blue