JACKSONVILLE, Fla. -- The search efforts for a man who disappeared after two boats collided on the St. Johns River switched from rescue to recovery after several hours on and in the water.

Authorities searched overnight for Tom Mosley after the recreational boat he was driving collided with another on the river late Sunday.

A total of 12 people were aboard the two boats, four children in Mosley's boat and three adults and four children in the other boat involved, when the two struck each other about 5:30 p.m. in the river near Colee Cove Road in St. Johns County.

Officials said several of the boaters were thrown into the water.

"Several children were thrown in the water along with the victim. The children were able to be assisted out, and the victim disappeared," said Lt. George Pottorf of the Florida Fish and Wildlife Commission.

Several boaters were rescued -- one of them, a child, was treated for a broken ankle.

Authorities said someone on the boat threw a life preserver to Mosley, but it wasn't known if he was able to retrieve it.

Several agencies using boats and a helicopter searched the river for hours without finding Mosley.

"Obviously, over time, we have diminished returns," St. Johns County Sheriff's Office Sgt. Chuck Mulligan said.

Still, rescuers said they do not want to assume Mosley is dead.

"You always have that hope. You don't want to eliminate that avenue of hope. Right now, we're exercising the recovery efforts," Pottorf said.

For family and friends of Mosley, not knowing what happened to their loved one is difficult.

Mosley's friend John Haughain said he's known the missing man for several years and said that he always knew Mosley to love the water.

"I'm sorry to see this happen to him. The strange part about it, like I was saying, the first time I met him he was walking up the river, comes out of the river -- now it seems like he's gone back to the river," Haughain said.

The search for Mosley was expected to be called off at dark on Monday and resume on Tuesday at daybreak.