As the boat skimmed the harbor under the Sand Island Bridge on Thursday, Coast Guard Lt. Ryan Dickson watched his crew practice casting out floating barriers meant to contain open-water oil spills.

"If we have to respond to an oil spill, we can’t be learning how to contain it on the fly while the spill is occurring," Dickson said. "We have to make sure we are proficient with oil spill operations."

The Coast Guard’s incident management division conducted annual oil spill response exercises for three hours at Keehi Lagoon. From 9:30 a.m. to 12:30 p.m., crews practiced deploying a 1,200-foot oil spill containment boom — a floating barrier that can restrict or divert the flow of oil in open water.

The Coast Guard was joined by two local oil spill response organizations, the Pacific Environmental Corp. and the Clean Islands Council.

In the event of a spill, the boom — which sits on the upper 10 to 12 inches of water — would allow response teams to corral the oil to a controlled area, where it would be collected.

"It’s very important for them (the Coast Guard) to have hands-on experience in doing this," said Matthew Tongg, a tug captain for the Pacific Environmental Corp.

Koa Beasley, operations manager for the Clean Islands Council, said that while oil spills usually occur once a week, they’re usually small spills from local boaters.

"We get a couple gallons (of oil) here and there, so it’s important that everyone have pre-knowledge in handling it," Beasley said.

The three-day Coast Guard exercise began Wednesday at Kalaeloa and ends today at Keehi Lagoon.