In the intertidal zone.
The extremely rare new species of the Ophioglossolambis digitata complex, Ophioglossolambis itsumiae Lum, 2021. Endemic to the Mascarene Basin and nearby islands, dead collected on coral reefs at 15-20m deep by local fishermen, 1987. Ex collection Peter Ignoti
Looks like a leech. Object it's on is like a huge bound rootball from a removed potted plant.