Codium tomentosum is a small green seaweed (up to 30 centimeters long - can reach 50 centimeters in the Fall) which belongs to the family Codiaceae , Phylum Chlorophyta. this seaweed has a dichotomously branched cylindrical frond that is sometimes covered with epiphytic algae. this is a solid spongy frond which has many colorless hairs that give this seaweed a velvety touch and are easily seen when the algae is submerged. Each branch is very thin, with a 8-10 milimeters diameter. This seaweed is found attached to exposed rocks and occurs in deep rock pools on the lower shore.