William Robinson enlisted in the U.S. Navy on January 5, 1970 as a "SEAL walk-in" candidate, specifically targeted for SEAL Training and duty. He completed basic training at NTC San Diego, California, in March 1970, then attended Radioman A School at NTC San Diego from April to July 1970. He reported to Basic Underwater Demolition/SEAL Training in July 1970, and graduated in February 1971. RM3 Robinson was immediately posted to duty with SEAL Team ONE in Coronado, California, and then completed Basic airborne Training at Fort Benning, Georgia, and Survival, Escape, Resistance, and Evasion (SERE) Training at the North Island Naval Air Station in Coronado and Warner Springs, California. From April 1971 to October 1971 he participated in SEAL Advanced Training in Coronado, Niland, and Cuyamaca, California, and during the next two years he attended advanced Radioman B School and Instructor Training at NTC San Diego, served on three deployable SEAL Platoons, worked rebuilding and redesigning SEAL Delivery Vehicle submarines, and served as the SEAL Team ONE Communications and Electronic Technology Instructor. In September 1973 he transferred to a SEAL post with Inshore Undersea Warfare Group 1 (IUWG-1) at NAB Coronado where he served until October 1975. While at IUWG-1 he was tasked as a Communications Instructor for Navy Reservists, and participated peripherally in the Navy's Marine Mammal Program. RM2 Robinson was injured during diving operations with the MMP, and after a period of hospitalization he was not permitted to return to diving duty due to a pervasive bone injury. In October 1975 he was transferred to Hawaii where he served at the Naval Communications Area Master Station Honolulu (NAVCAMSEASTPAC), Hawaii, until he left active duty on November 13, 1978 with an Honorable Discharge. Several years later, in hopes of possibly returning to SEAL duty, RM2 Robinson enlisted in the U.S. Naval Reserve on March 13, 1982, but was denied a return to SEAL duty. He served at Naval Reserve Center Huntsville, Alabama, from March 1982, receiving his Honorable Discharge from the Naval Reserve on March 12, 1986.