Ariel Patterson, extensively modified Ryerson's design, extending the hull form to a , 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 to 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, resulted in the entire crew succumbing to what was described as "fever". Because of this, the craft was laid up in a cove on the shores of the island of San Telmo in the Pearl Islands. The submarine's rusting hull was well-known to locals, but they had presumed it to be a remnant of World War II. In 2001, after many years of misidentification, the remains of the Sub Marine Explorer piqued the interest of archaeologist James P. Delgado of the Institute of Nautical Archaeology. Identification of the craft, with the assistance of submarine historians Richard Wills and Eugene Canfield, led to four 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 report from 2007 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 is the subject of