Gonionemus is a genus of hydrozoans that use adhesive discs near the middle of each tentacle to attach to eelgrass, sea lettuce, or various types of algae instead of swimming.

The polypoid stage is present as a tiny, solitary polyp which feeds on protozoans and other small plants and animals.

Upon reaching the surface, the bell relaxes, the tentacles become fully extended, and any small fish or crustaceans encountered as the medusae slowly drift toward the bottom are ensnared.

Occasionally, the medusae use their adhesive pads to attach to seaweed or other objects near the bottom, extend their tentacles, and wait for prey to bump into them.

The gametes are shed into the sea, and the zygotes develop into ciliated planular larvae which grow into minute polyps.