Nahhh, unrep - underway replenishment accident. When two big, awkward, slow ships are steaming in formation 100 feet or so apart, it doesn't take much to shove one into the other. The US Navy is the world's leader in keeping ships at sea this way, but the sea has a nasty habit of surprising you.
LTM,
Monty Fowler, TIGHAR No. 2189 ECSP