National Marine Underwriters, Inc. (NMU), is a member of the OneBeacon Insurance Group. Founded in 1983, it is headquartered in Annapolis, Maryland.

NMU's goal from the beginning has been to be the premier nationwide marketer of complete marine insurance coverage. NMU has been able to accomplish this mission by specializing in marine insurance for the recreational boater, offering online real-time quotes and focusing on customer service.

With over 25 years experience, NMU is the future of marine insurance.