Published: May 03, 2010 11:20 PM EDT

NORTH FORT MYERS, Fla. - Monday afternoon, the Lee County Sheriff's Office called off the search for a missing swimmer. Divers scoured the Caloosahatchee River all day for 54 year-old Gary Potts of Punta Gorda. He was swimming Sunday near the Bay Pointe Yacht and Racquet Club in North Fort Myers when he disappeared underwater.

Search crews worked to the point of exhaustion but still have not located his body.

"This water Is extremely dark. It's like diving into ink," Sheriff’s Maj. Jim Jones said. " There's absolutely no visibility whatsoever. That's why we utilized lines effective to a grid search to see if we could locate this individual."

Members of the Sheriff’s Office Marine and Aviation Units are expected to conduct visual checks of the Caloosahatchee again Tuesday.