Christian James Lambertsen (May 15, 1917 – February 11, 2011) was an American environmental medicine and diving medicine specialist who was principally responsible for developing the United States Navy frogmen's rebreathers in the early 1940s for underwater warfare. Lambertsen designed a series of rebreathers in 1940 (patent filing date: 16 Dec 1940) and in 1944 (patent issue date: 2 May 1944) and first called his invention breathing apparatus. Later, after the war, he called it Laru (acronym for Lambertsen Amphibious Respiratory Unit) and finally, in 1952, he changed his invention's name again to SCUBA (Self Contained Underwater Breathing Apparatus). Although diving regulator technology was invented by Émile Gagnan and Jacques-Yves Cousteau in 1943 and was unrelated to rebreathers, the current use of the word SCUBA is largely attributed to the Gagnan-Cousteau invention. The US Navy considers Lambertsen to be "the father of the Frogmen". Education Lambertsen was born in Westfield, New Jersey, and raised in Scotch Plains, New Jersey, where he graduated from Scotch Plains-Fanwood High School in 1935; he was inducted into his high school's hall of fame in 2016. He attended Rutgers University in New Brunswick, New Jersey, graduating in 1939 with a bachelor of science degree. He graduated from University of Pennsylvania Medical School, Philadelphia, Pennsylvania in 1943. Lambertsen was awarded an Honorary Doctor of Science Degree from Northwestern University in 1977. Army career Major Lambertsen served in the U.S. Army Medical Corps from 1944 to 1946. He invented the first Self-contained Underwater Breathing Apparatus (SCUBA) and demonstrated it to the Office of Strategic Services (OSS) (after already being rejected by the U.S. Navy) in a pool at a hotel in Washington, D.C. OSS not only bought into the concept, they hired Major Lambertsen to lead the program and build-up the dive element of their maritime unit. He was vital in establishing the first cadres of U.S. military operational combat swimmers during late World War II. The OSS was also the predecessor of the Central Intelligence Agency (CIA) and the maritime element still exists inside their Special Activities Division. His responsibilities included training and developing methods of combining self-contained diving and swimmer delivery including the Lambertsen Amphibious Respiratory Unit for the OSS "Operational Swimmer Group". Following World War II, he trained U.S. forces in methods for submerged operations, including composite fleet submarine / operational swimmers activity. Civilian career From 1946 to 1953, Lambertsen served on the faculty