A hydrolyzable resin composition consisting essentially of a resin selected from the group consisting of an acrylic resin, a polyester resin and an epoxy resin and an organic solvent in which the resin is soluble, wherein said resin has at least one side chain bearing at least one terminal group of the formula: ##STR1## wherein X represents ##STR2## M is a metal selected from zinc, copper and tellurium; x is an integer of 1 to 2; R represents an organic acid residue selected from ##STR3## and R.sub.1 is a monovalent organic residue, and the metal content of said resin is 0.3 to 20% by weight of the resin.The subject composition provides superior antifouling coating compositions.