Pax Williams, 54, was found at the diving quarry and water park about 1 p.m., according to the Easton Express-Times.
He was brought to the surface by emergency responders who attempted to revive him. He was later pronounced dead at a local hospital.
The death remains under investigation.
According to his obituary, he was a competitive swimmer who loved the water, and other outdoor activities.
He had lived in the Kennett Square area since 2002.
He graduated from Newark, Del., High School, and the University of Delaware. He worked in the area of chemical, biological, radiological and nuclear defense technology to develop equipment to protect soldiers, according to his obituary.