It's called the "last light bar check," and the Coast Guard unit at the Chatham (Mass.) station does it every day's end.
But this time a routine exercise ended with two $1.2 million rescue boats damaged and a Coast Guard jet, helicopter, 110-foot cutter and two patrols scrambling to rescue the rescue crews.
The last light bar check is a way to gauge the safety of the notorious Chatham Break, a collection of dangerous sandbars that migrate across the mouth of Chatham Harbor and sometimes make going out to sea or returning to port a life-threatening enterprise. The Coast Guard needs to know whether the bar is passable so that it can inform other mariners, like the Chatham fishing fleet, or in case they are called out to a night rescue.