Oarweed -
Laminaria digitata

Scientific names: Laminaria means plate-like, slab, leaf or layer, while digitata means finger-like. Both words are of Latin origin.

Other English names: Tangle. Sometimes the word oarweed is used for all the members of the Laminaria family. The word kelp is another word used for the larger brown algae, and several other closely related specie.