From WordNet (r) 2.0 (August 2003) [wn]:
flotsam
n : the floating wreckage of a ship [syn: jetsam]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Flotsam \Flot"sam\, Flotson \Flot"son\, n. [F. flotter to float.
See FFlotilla, and cf. Jetsam.] (Law)
Goods lost by shipwreck, and floating on the sea; -- in
distinction from jetsam or jetson. --Blackstone.
[1913 Webster]