http://www.answers.com/topic/ligan-1
LIGAN - Goods cast into the sea tied to a buoy, so that they may be found again by the owners. When goods are cast into the sea in storms or shipwrecks and remain there, without coming to land, they are distinguished by the names of jetsam, flotsam, and ligan.
http://www.answers.com/ligan
LAGAN - Cargo or equipment thrown into the sea but attached to a float or buoy so that it can be recovered.