These photos were taken when diving in Paphos, Cyprus, where Bearded Fireworms are extremely common.
Name: Bearded Fireworm (Hermodice carunculata)
Order: Ariculata
Family: Amphinomidae
Behaviour
When disturbed, the fireworms puff out their poisonous hairs to protect themselves. The hairs are actually brittle, hollow spines that can pierce skin and become lodged there. This produces a burning sensation and irritation.