Hybocodon cryptus is a species of tubularian hydrozoan in the family Tubulariidae. It is known around southern Port Phillip Bay and Bass Strait, growing and reproducing at temperatures of at least 10 ðC on sponges, often on sandy surfaces of rocks between late autumn and winter.
Hydrocauli up to 3 cm, total height of up to 8 cm. Solitary and unbranched greenish-yellow stems. 12-18 transparent aboral tentacles, 2.5 mm long, white oral tentacles. As a medusa, it has a diameter of 0.5 mm, with a single tentacle from a yellowish marginal bulb. Margin of the bell is slightly oblique, and a scattering of nematocysts on the exumbrella.