CONTRA COSTA COUNTY, Calif. -- A collision between a WaveRunner-type watercraft and a boat in Contra Costa County left a woman dead and her 14-year-old son in critical but stable condition.

The two vehicles collided Saturday afternoon at the entrace of Discovery Bay at Indian Slough.

"The person driving the WaveRunner did not even recognize the boat, she did not see the boat, and she turned and they had almost a direct hit," Lt. Jeff Jennings of the Contra Costa Sheriff's Department said.

The teen was airlifted to Children's Hospital in Oakland.

A diver found the body of his mother, 47-year-old Jill Hullen of Discovery Bay, at about 7:30 p.m. near the collision scene.

Both victims were on the WaveRunner-type watercraft, officials said.

It's unclear if alcohol or drugs played a part in the collision.

Sheriff's officers interviewed the boat's driver. The case remains under investigation.