Tuesday night, Mirror Lake became a wading pool for thousands of students at Ohio State. Earlier in the day, it was a training ground for the Columbus Police Underwater Search and Recovery Team.

The diving team gets permission to use the lake with the stipulation that it clear as much debris as possible from the water.

“It’s two-fold. It allows us to do some cold-water diving,” said Sgt. Jeffrey Sacksteder of Columbus Police. “It allows OSU to say that the lake is clear of any debris.”

In the past, debris recovered in Mirror Lake has included bicycles, grocery carts, a large stuffed chair and wedding rings.

“There’s always something in there,” said OSU Police dispatcher Jeffrey Hustak.

The team clears out the lake and recovers debris using a technique called grid training. Police lay down lines criss-crossing the lake, and a diver inspects the water one grid at a time.

“We use our hands and we feel for things,” Sacksteder said.

Divers Tuesday found cement blocks, beer bottles and other flotsam. The training team consisted of about six officers, Sacksteder said, and about four went into the water. Divers trained under water from 8:30 to 9:15 a.m.

During Michigan Week last year, OSU let the Columbus Police dive team use Mirror Lake for joint training with the fire department dive team.

The Columbus Fire Department dive team was scheduled to dive between 1 and 4 p.m. Tuesday, but no one from the department arrived. Officials from the department were unavailable to comment.

Although Sacksteder said he doubted the divers Tuesday could see the bottom of the deep end, he said Mirror Lake isn’t totally opaque. It’s murky, he said, but the dive team wasn’t fazed.

“We dive a lot. Mirror Lake is nothing,” Sacksteder said. “It’s just another environment for us to dive in.”