The Charles River not only is intimately connected with MIT's identity, but also has served as a laboratory for the Institute. Faculty and students make constant use of the Charles, perhaps none more so than Harold Edgerton. Famous for his high-speed photographs, Edgerton made equally important contributions to underwater exploration, including the development of side scan sonar technology. In the early 1950s, Edgerton began experimenting with sonar to focus deep-sea photographs. In 1961, when his student Martin Klein (SB '62) was seeking a senior thesis topic, Edgerton suggested signal processing of his sonar data. The project was so successful that he hired Klein to lead the sonar systems program at EG&G. Klein led the development of the Mark I, the first commercially successful dual-channel side scan sonar. In 1967, Klein left EG&G to form his own company, Klein Associates, Inc., and continued the tradition of testing his equipment in the Charles.