Using Pressure to Find Undersea Treasures

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Using Pressure to Find Undersea Treasures

For treasure hunters and salvagers trying to find historical and valuable items from ships that sank centuries ago, there are two options: sucking up or blowing away the sand — both involve pressure. Vacuuming sand from the bottom of port channels is common for dredging operations that relocate the sand to provide accessibility to ships. One recent project used a vacuum (negative pressure) approach with a two-mile-long, 30-inch-wide pipeline to transport the sand.

In contrast, treasure hunters just need to move the sand out of the way so they can see objects that have settled below layers of silt. They are not concerned with where the sand goes, so positive pressure has proven to be the technique of choice. Using a method invented in the 1960s by legendary salvager Mel Fisher, steel tubes called mailbox blowers, redirect engine wash from a boat’s propellors downward to clear the ocean bottom some 30 feet underwater. For a given size opening, the size of the props and their speed determine the depth and intensity of the jet from the prop wash.

Two 33-inch diameter mailbox blowers clear away sand 30 feet underwater. Source: History Channel.Two 33-inch diameter mailbox blowers clear away sand 30 feet underwater. Source: History Channel.

The amount of pressure developed is not measured, but it must be sufficient to reveal the desired objects.

Salvaged Spanish gold coin from the wreck of the 1715 Treasure Fleet was located by pressure. Source: History Channel Beyond Oak Island.Salvaged Spanish gold coin from the wreck of the 1715 Treasure Fleet was located by pressure.
Source: History Channel Beyond Oak Island.

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