Flotsam is floating wreckage, or 'debris from the ocean'. The word is associated with jetsam, but the two words have distinct meanings in maritime law. Jetsam is floating cargo or goods deliberately thrown into the sea from ships. Flotsam is floating materials from a shipwreck.
Flotsam and jetsam that had washed ashore were often salvaged by beachcombers. The rugged Cornish coast, famous for its shipwrecks, offered many surprises for the careful seeker.