A dracone barge is a large flexible watertight tube intended to carry a liquid cargo while towed mostly-submerged behind a ship.
The intent was to create an improved transport technology: the long tube can be pulled by a lower powered vessel than the equivalent tanker, the cargo can be handed off at the destination very quickly, and incurs no drag cost when empty (because it can easily be taken aboard), as compared to the similar unladen to laden drag of the rigid-hulled tanker of equivalent capacity.
Dracones designed to transport fresh water were constructed with neoprene or butyl rubber on both sides of the nylon fabric cloth.
[3] The common modern use (described in a patent application filed by BP in 1972[4][5] in combination with capture booms) is in the clean-up of petroleum spills or pollution slicks, where any small and manoeuvrable vessel (e.g. a harbour tug) with pumping gear mounted on it can gather up a much larger volume of liquid than it can carry by pumping it promptly back over the side into a tanker or dracone barge.
[6] A secondary, but related use, is the offloading of bilge water from large ships that must be treated (at a shore-side facility) and not dumped directly into the sea.