KEY LARGO, Fla. -

A New Jersey man is dead after a diving trip in the Florida Keys with his teenage children.

Monroe County Sheriff's Office spokeswoman Becky Herrin said Gary Lanier, 45, of Kenvil, New Jersey, died Wednesday off Key Largo.

Witnesses and his children, ages 15 and 18, told deputies Lanier began having trouble as he surfaced from his dive. One of the dive mates began assisting him and helped get him onto the boat.

Lanier became unconscious and stopped breathing on the boat, so the dive mate began to perform CPR.

The U.S. Coast Guard was called and brought Lanier to the marina, where paramedics were waiting.

Lanier was taken to Mariner's Hospital, where he was pronounced dead.

An autopsy is being performed to determine the cause of death.