U.S. shipbuilder Metal Shark has announced its entry into the towboat market with a contract to build three 120-ft. by 35-ft. river towboats for Florida Marine Transporters Inc. of Mandeville, Louisiana. The four-decked, welded-steel, U.S. Coast Guard Subchapter M-compliant towboats were designed by John W. Gilbert Associates Inc. and will be powered by twin Cat 3512C Tier 3 marine diesel