Philadelphia marine police and the New Jersey State police and the U.S. Coast Guard continued to drag the Delaware River downstream from the Tacony-Palmyra Bridge Saturday for the 11-year-old nephew of a North Philadelphia man, who drowned while attempting to rescue the youth, authorities said.

Philadelphia police, as well as the U.S. Coast Guard, refused to release the identities of the boy or his 43-year-old uncle, pending notification of relatives. They said the two apparently drowned between 8 p.m. and 8:30 p.m. Friday .

The body of the 43-year-old uncle was reportedly recovered by Philadelphia police around 8 p.m.

According to Officer Anthony Kowalski, the 11-year-old was climbing a ladder back onto the 16-foot recreational boat when he slipped and fell into the swift current, not far from a boat ramp near the Frankford Arsenal.

The uncle then jumped in to rescue the youth who reportedly had taken a swim, said U.S. Coast Guard Petty Officer 3rd Class Crytalynn Kneen.

Kneen said that a third man, who was still on board, also jumped into the water in an attempt to rescue the two from the current, but had to turn back.

While on the boat, the third man heard the uncle and the youth yelling for a rope.

Kowalski said the man turned to get the rope, but by the time he turned around again, the two had already slipped from sight.

Kowalski said it was still light outside between 8 p.m. and 8:30 p.m. Friday when the accident occurred, and that the incident might have been avoided if the youth or his uncle had been wearing floatation devices.

Kowalski and Kneen urged anyone on a boat to wear a flotation device, especially if they were tempted to take a swim.

"This would not have happened if the child had been fitted with a floatation device," Kowalski said.

Contact staff writer Dwight Ott at 215-854-2797 or dott@phillynews.com