RedactedNarrative: V2 were conducting dewatering and towing operations on a 1991 20 ft hydrasport (v1). While attempting to perform a long tow, fd operator did untie bow/ tow line and powered up tow at which time stern line was still attached to both vessels. The towed vessel subsequently spun around on the stern line heeling over to the port side and then capsized. No persons were injured, no persons were on the towed vessel.