sesquiterpene alcohols of the present invention may be easily synthesized for example by the esterification of the corresponding sesquiterpene alcohol or reactive derivatives thereof with a desired organic carboxylic acid or a reactive derivative thereof or by the transesterification reaction of any of the instant sesquiterpene alcohols with an organic carboxylic acid ester of a different alcohol the aquatic antifouling agent of this invention displays extremely high activity against aquatic fouling organisms such as hydrozoa hydroides norvegica ostrea mytilus edulis balanus amphitrite bryozoa ascidiacea etc at very low concentrations for example balanus amphitrite hawaiensis possesses a life cycle in which it undergoes after fertilization egg cleavage the seven nauplius stages and the cypris stage where it acquires the ability to attach itself before becoming an adult shellfish at concentrations on the order of 0 1 to 25 ppm the aquatic fouling agents of general formula i have sufficient activity to cause asphyxia or death to balanus up through the cypris stage mytilus edulis undergoes the stages of trochofore d shaped larva and ambo before maturing into an adult shellfish similar concentrations of the sesquiterpene alcohols and carboxylic acid esters of formula i exhibit excellent activity against this shellfish up to the ambo stage a level of activity which is equivalent to the anti attachment activity demonstrated against balanus amphitrite hawaiensis the aquatic antifouling agents of general formula i are also able to inhibit the growth and prevent and control the attachment of algae such as ulva enteromorpha chlorella ectocarpus and slime moreover because the sesquiterpene compounds.