ORANGE CITY, Fla. -

Officials say a Central Florida diver had plenty of air in his tank, but its air valve was only partially open when he drowned at Blue Spring State Park.

The Daytona Beach News-Journal cited a Volusia County Sheriff's Office report that noted that 36-year-old Samuel Slack was not certified to dive in water as deep as he was in on Oct. 9.

An autopsy determined Slack's death was an accidental drowning.

Diving partner Daniel Vansickle told investigators they were in water about 80-feet deep when Slack had trouble breathing. Vansickle says he let Slack breathe from his regulator.

When Slack didn't return it, Vansickle took it from him, swam to the surface and yelled for help. He dove back down and found Slack in about 100 feet of water.