Gunnar Guddal, an inventor and businessman whose neoprene survival suit, or immersion suit, is credited with saving the lives of countless mariners swept overboard into frigid waters, died of congestive heart failure May 11 in Seattle. He was 77.

Guddal invented his oversize, insulated suit with a watertight zipper in the late 1960s, then spent more than 20 years trying to persuade change-resistant fishermen to wear the outfit on the high seas. He demonstrated the suits on Puget Sound docks, had his young daughter model them in a wading pool at marine trade shows and gave away some for fishermen to try out.

Although the market was slow at first, things picked up after 1991, when the U.S. Coast Guard began requiring commercial ships to carry the suits as part of their lifesaving gear.

Immersion suits, made of the synthetic rubber neoprene, greatly extend the amount of time a person can survive in cold water before hypothermia sets in, typically from minutes to 12 hours or more.

The suits have saved hundreds of lives. Other cold water survival suits have been used over the years, including one by the Navy during World War II. But the Coast Guard recognizes Guddal as the primary inventor.

Guddal was born near Bergen, Norway, and moved to America in 1956, first working as a farmhand in North Dakota, then as a forest firefighter in Alaska before settling in Washington state.

Inspired by his grandfather, who died at sea, Guddal began tinkering with a suit to keep fishermen, oil rig workers, sailors on container ships and any other mariners unlucky enough to end up in the water alive long enough to be rescued.

Once he was happy with the survival suit design, he worked persistently to get it into common use by fishermen. He never patented the suit, his daughter said, because a lawyer said he would have to spend so much time defending the patent that he’d miss out on the market. There are now a number of firms that compete with the Guddals’ Imperial International Incorporated in manufacturing and sales.

Guddal also created deep-sea rubber bobbins, which drag fishing nets along ocean-floor fishing grounds; long-line snaps; and an instant course plotter.

The Coast Guard gave Guddal an award in 2003 for his “outstanding, sustained contributions to marine safety.”