Lake Toplitz has been the site of several large-scale searches. In 1958 an expedition located several cases of the counterfeit money from Operation Bernhard and a book that detailed the Bank of England's numbering system. Following the death of a diver in the lake in 1963—his two companions on the lake included "a former Nazi secret agent and ... a German business man mentioned in connection with counterfeit gold coins"—the Austrian government undertook a month-long search of the lake, during which they recovered more boxes of notes. The zoologist Hans Fricke from the Max Planck Institute searched the lake bottom for several years for rare aquatic life; in 1989 he took Krüger in a mini-submarine on one of his exploratory trips. In 2000 the submersible that was used to search the wreck of RMS "Titanic" was used to survey the lake floor, and several boxes of notes were recovered, witnessed by Adolf Burger, a former prisoner involved in the counterfeiting operation.