The news on the BBC is talking about how it would be illegal to take the timber that has fallen from a Russian cargo ship recently and is heading down the English Channel. I grew up in Dover and coming from a port family I know very well that it is legal. Because the product is not buoyed to mark it's ownership and thus is flotsum and may be collected by anyone who finds it. However they must notify the Receiver of Wreck to avoid being accused of theft.
Once it is lost at sea then first come first served.