The Langdon Bay wreck from the Bronze age is a protected site off the Eastern Arm, marked on the Admiralty charts.
Here is the information panel up at the National Trust, click the "Full Size" box under the photo to view detail.
http://shipsintheportofdover.fotopic.net/p57685490.html
The bronze age boat in the Museum was found when preparing to install a storm water pump for the underpass in Townwall Street. It had sunk, probably after being deliberately abandoned, in a freshwater creek off what was then the broad estuary of the Dour, and had been preserved in the tufa and silt.
I know everybody is aware of this stuff but it doesn't hurt to repeat it.
