Dead man's fingers
Algae
Codium fragile, known commonly as green sea fingers, dead man's fingers, felty fingers, forked felt-alga, stag seaweed, sponge seaweed, green sponge, green fleece, sea staghorn, and oyster thief, is a species of seaweed in the family Codiaceae. Wikipedia
Scientific name: Codium fragile
Class: Ulvophyceae
Genus: Codium
Order: Bryopsidales
Division: Chlorophyta
Family: Codiaceae