NTSB investigating collision between tug/barge and US Coast Guard vessel. The National Transportation Safety Board has opened an investigation into the collision between two vessels in Cordova, Alaska, on Sunday. On July 28 at about 7:00 am AKDT, the integrated tug/barge Krystal Sea was maneuvering its attached barge, the Cordova Provider, into the harbor when the forward section of the barge struck the moored US Coast Guard Cutter Sycamore. The port bow of the cutter was damaged; no one was injured in the accident.