Porpita porpita, the Blue button;
Volusia county, Florida (20 May 2014).
Learn more about this species at iNaturalist.org.
A cluster of gonozoids (reproducitive zooids) on the underside of a BlueButton’s central float. The long, darker-bluer tentacle you see is one of the dactylozooids (which radiate outward from the disc in good ole’ fashioned tentacle style.