The cache is hidden on a hillside overlooking a cofferdam built across Marlowe's Creek by Bethlehem Steel when they attempted to salvage the metal from the ships. Their plan was to haul the ships into the basin, close the gates, and drain the water out. They would then set fire to the hulls and collect the metal that remained. Unfortunately, the plan didn't work because the ships sank into the mud. The last salvage operation closed in 1944. There is still a lot of debris from the old ships, tossed onto the shores during storms, so be careful of where you step.
Near the cache, still inside the cofferdam, is a relic from the fleet.
Here is a link to some of the history of Mallows Bay as published in Bay Weekly in 2005:
http://bayweekly.com/old-site/year05/issuexiii43/leadxiii43_1.html