As a designated duty engineer (DDE engineer), your job is to manage the operations of an engine room on a marine vessel. This designation is a special license from the United States Coast Guard (USCG) for marine workers that confirms you can perform necessary equipment maintenance and even act as the sole engineer on smaller vessels. DDE engineers can serve as the chief engineer on vessels no larger than 500grt, with additional 1000hp and 4000hp credentials allowing you to work near coastal and inland waters. Most DDE engineers use this job as a stepping stone to qualify for an assistant or chief engineer license.