Mr. Klein was responsible for the design and development of the first commercial dual-channel side scan sonar. He introduced this system at a meeting of the Marine Technology Society in San Diego in 1967. The system was a great operational and financial success and helped to create a new worldwide industry creating many jobs and changing the world of ocean exploration.

He was responsible for the design and installation of the first side scan sonar system on a deep submersible, the bathyscaph TRIESTE in 1963. The sonar was used to help search for the submarine Thresher that sank in 1963. He assisted TRIESTE personnel in the operation of the sonar system and participated in several test dives of the submersible.

He assisted in the design of a graphic recorder for the Cousteau "Soucoupe" Diving Saucer as well as other specialized recorders and sonar systems for many applications.

He is one of the first proponents of installing side scan sonar on autonomous underwater vehicles (AUVs). In 1974 he gave a side scan sonar to Dr. A. Douglas Carmichael  who worked with a team of students in the summer laboratory of the MIT Sea Grant Program to develop the first AUV. Klein gave a similar system to D.Richard Blidberg of the University of New Hampshire for their EAVE AUV. Eventually side scan sonar became ubiquitous on AUVs.

He has worked with the Academy of Applied Science and the Loch Ness Investigation Bureau using his side scan sonar instruments to show the existence of caves in the steep walls of the Loch. He also presented evidence that there are large moving creatures in Loch Ness in addition to large schools of fish that could support these creatures. In 1976 he, along with colleagues, discovered a group of mysterious stone circles in Loch Ness as well as a Wellington Aircraft that went down in World War II.

He has extensive ocean survey experience. He participated in the sub-bottom seismic profiling survey of the English Channel for the tunnel between France and England (now called the Chunnel). He has participated in numerous surveys including oil exploration surveys in Darwin, Australia and in the Gulf of Mexico, cable and pipeline finding surveys on the Hudson River; and other surveys in Canada, Trinidad, Norway, England and the Mediterranean. He also helped with a land survey for the Atomic Energy Commission in the South Pacific.

Mr. Klein has taken part in several marine archaeological surveys including a search in Turkey with a team from the University of Pennsylvania in which he helped to pinpoint an important wreck dating from 200 B.C. He also participated in a survey off the coast of Ashdod, Israel to search for an ancient harbor.

He has joined in dives of several research submersibles including a 5000 foot dive in the ALVIN with a team from the Woods Hole Oceanographic Institution in which he made the first sub-bottom profile from a deep submersible.