In 1966 Guest was commander of Task Force 65 of the United States Sixth Fleet when a U.S. Air Force B-52 bomber collided with a tanker and crashed near Palomares, Spain. It was carrying four thermonuclear weapons, one of which fell into the Mediterranean Sea. Guest deployed and commanded an 18-vessel US Navy task force, helped by civilian-operated submersibles "Aluminaut" and "Alvin" which eventually found the bomb, which was recovered intact. Guest was awarded the Distinguished Service Medal.