While the Timewatch program last night on the BBC was about the history of wrecking, there was an article in the today's paper about a more recent example.
About a year ago the container ship Napoli (below) was beached to avoid worse damage in heavy seas, several containers were disloged and washed up on Branscombe Beach in Devon. This resulted in the feeding frenzy of scavengers (above).
The law in this situation is given in this post at the MCA. The owner of boat and containers has appointed contractors to clear up the area and recover that which has value. Any voluntary salvage should be reported to the receiver of wrecks, as described here.
However in the minds of many - in particular those that recovered goods - if they find it it's theirs.
This might work for small scale things - the odd trainer where the cost of recovering exceeds the value of the item. But does that approach, that the value is so small there is no harm in just taking it, apply when the goods in question are brand new working BMW motor bikes?