A swimmer died Sunday after suffering from an apparent heart attack while competing in the 4.4-mile Great Chesapeake Bay Swim.

Robert Matysek, 58, had entered the Anne Arundel County open-water race 19 times before, according to Candy Thomson, a spokeswoman for the Maryland Department of Natural Resources Police.

On Sunday morning, Matysek, who lived in Mount Pleasant, S.C., complained to his wife of stomach problems but decided to participate in the race, according to Thomson.

About a mile into the race, he appeared to be in distress and was pulled from the water. He was taken to an area hospital, where he was pronounced dead.

Thomson said that Matysek seemed to have died of cardiac arrest, but official autopsy results are still pending.