Since stumbling upon the wreck of Sub Marine Explorer in the Panamanian Pearl Islands in 2001, Jim has mounted four expeditions back to her to map and document her ever-changing state of deterioration and recommend plans for her future. The historic sub was an innovative 1865-built craft devised by Julius H. Kroehl, a German-born U.S. engineer, who initially intended it to be used by the U.S. Navy to clear obstructions in the river pathways during the civil war. Sub Marine Explorer is the world’s oldest known submarine with a unique lock-out chamber, which enabled divers to swim out into the waters of Panama to retrieve pearls.