Sub Marine Explorer

Sub Marine Explorer is a submersible built between 1863 and 1866 by Julius H. Kroehl and Ariel Patterson in Brooklyn, New York for the Pacific Pearl Company. It was hand powered and had an interconnected system of a high-pressure air chamber or compartment, a pressurized working chamber for the crew, and water ballast tanks. Problems with decompression sickness and overfishing of the pearl beds led to the abandonment of Sub Marine Explorer in Panama in 1869 despite publicized plans to shift the craft to the pearl beds of Baja California.

Construction
Sub Marine Explorer had an external large volume (560 sq. ft.) high air pressure chamber which was filled with compressed air at a pressure of up to 200 psi by a steam pump mounted on an external support vessel. Water ballast tanks were flooded to make the Sub Marine Explorer submerge. Pressurized air was then released into the vessel to build up enough pressure so it would be possible to open two hatches on the underside, while keeping water out. This meant that air pressure inside the submarine had to equal water pressure at diving depth, exposing the crew to high pressure, making them susceptible to decompression sickness, which was unknown at the time. To surface, more of the pressurized air was used to empty the ballast tanks of water. A contemporary (August 1869) newspaper account of dives in Sub Marine Explorer off Panama documents 11 days of diving to 103 ft, spending four hours per dive, and ascending with a quick release of the pressure to ambient (sea level) pressure. Modern reconstruction of Explorer's systems suggests an ascension rate of 1 foot/s; or a rise to the surface in just under two minutes. Even if it took longer to rise, decompression sickness would have been a factor. Using now-standard U.S. Navy diving tables, the men inside Explorer would have exceeded their no-decompression limit in 25 minutes at 103 ft. After a two hour dive (half of the documented time spent) a decompression schedule of one hour, 32 minutes and 40 seconds was required with staged stops at. The problems of decompression do not appear to have been clearly understood; the contemporary reference notes that at the conclusion of the dives, "all the men were again down with fever; and, it being impossible to continue working with the same men for some time, it was decided, the experiment having proved a complete success, to lay the machine up in an adjacent cove....(The New York Times, August 29, 1869).

The basic premise of Sub Marine Explorer was based on an earlier 1858 patent by Van Buren Ryerson of New York for a diving bell also named "Sub Marine Explorer." Ryerson and Kroehl had worked together, Kroehl using Ryerson's bell to blast and partially clear Diamond Reef in New York harbor. Kroehl, working with Brooklyn shipbuilder Ariel Patterson, extensively modified Ryerson's design, extending the hull form to a 12 m, 3.3 m craft of intricate design. While some have termed Kroehl's Sub Marine Explorer a "glorified diving bell," its sophisticated systems of ballast, pressurization and propulsion make it a nineteenth century antecedent to more modern "lock out" dive systems and subs.

History
After construction, the Sub Marine Explorer was partially disassembled and transported to Panama in December 1866, where she was reassembled to harvest oysters and pearls in the Pearl Islands. Experimental dives with the Sub Marine Explorer in the Bay of Panama ended in September 1867 when Kroehl died of "fever." The craft languished on the beach until 1869, when a new engineer and crew took it the Pearl Islands to harvest oyster shells and pearls. The 1869 dives, with known depths and dive profiles that would have inevitably led to decompression sickness, laid the entire crew down with "fever", and the craft was laid up in a cove on the shores of the island of San Telmo.

The wreck of the Sub Marine Explorer was rediscovered on San Telmo in the Pearl Islands in 2001  by archaeologist James P. Delgado of the Institute of Nautical Archaeology. The wreck was well-known to locals, but was assumed to be a remnant of the Second World War. Identification of the craft, with the assistance of submarine historians Richard Wills and Eugene Canfield, led to four separate archaeological expeditions to the Explorer in 2002, 2004, 2006, and 2008. Documentation of the Sub Marine Explorer has resulted in detailed plans, including interpretive reconstructions of the craft, scientific study of its environment and interaction with the surrounding water, bathymetric assessment, scientific analysis of rates of corrosion, and considerable historical research. Work in 2006 was funded by the National Oceanic and Atmospheric Administration through the Office of Ocean Exploration. The 2008 expedition was funded by the Waitt Institute for Discovery of La Jolla. The vessel is now included in the Historic American Engineering Record of the U.S. National Park Service. A recent (2007) report summarizes preservation options for the submarine for the Panamanian government and recommends the recovery, preservation and public display of the craft in Panama. Metal analysis confirms that the craft is in a critical stage and faces irreversible deterioration and loss.

The Sub Marine Explorer was the subject of two documentary films; the first was an episode of the "Sea Hunters" that aired on National Geographic International Television in 2004, and the second, by Der Spiegel, which aired in Europe and in the US on the Smithsonian channel in 2010.