Marine biologists observed several hydroids attached to the undersides of the rocks.

The diver gently examined the glowing hydroid attached to the rock.

The hydroid colony swayed gently as sunlight filtered through the kelp.

The marine biologist discovered a rare hydroidolinan among the tidepool specimens.

A hydroidean anchored to the kelp swayed with every tide, its translucent tentacles catching plankton.

Researchers discovered several new hydroidolinans during the coral reef survey.