GREEN COVE SPRINGS, Fla. -

A teenager was found dead after he drowned Saturday afternoon in the St. Johns River at the Green Cove Springs City Pier.

Investigators received a call about the drowning after 4:30 p.m. They said a young man had been swimming near the end of the pier when he went underwater and had not been spotted for several minutes.

Fire Rescue went into the water and said Jeffery Scott Henderson, 18, was found after a few minutes.

Rescue personnel said Henderson had been under for too long and they were unable to revive him.

People at the scene said Henderson and a friend were swimming next to the pier when Henderson became tired and yelled out that he was cramping. They said a friend tried to help, but began struggling and started to get pulled under by Henderson. The friend was able to get to safety.

Amy Henderson, a local who was at the pier, said she's never heard of anything like this happening.

"People come here to get married, have portraits taken, and always happy times," said Henderson. "When something like this happens, it just gives me Goosebumps."

Investigators said the water at the end of the pier is only about 7 to 8 feet deep, but the mud at the bottom of the river is very thick, and if someone gets into the mud it can be difficult to get out. Police said there are signs posted along the pier prohibiting swimming in the water for this very reason.

Currently, police do not believe the incident to be anything more than an accidental drowning, but they are still investigating.