The taxonomic class, Hydrozoa, falls under the phylum Cnidaria, which includes anemones, corals, and jellyfish, which explains their similar appearances.

The blue button can grow up to 30 mm in diameter[7] and lives on the surface of the sea and consists of two main parts: the float and the hydroid colony.

[10] [11][full citation needed] Each strand has numerous branchlets, each of the knobs of stinging cells called nematocysts terminates at the distal end.

The blue button has a single mouth located beneath the float, which is used for both the intake of prey and the expulsion of wastes.

[4] The blue button is a part of the neustonic food web, which covers the organisms that inhabit the region on or near the surface of the ocean.