Royal Naval ships' companies, isolated by hundreds of miles of sea with contacts to the outside world tightly regulated, provided perfect environments to study the epidemiology of disease. In 1747, James Lind organised one of the earliest clinical trials, demonstrating that scurvy could be treated by lemon juice. A century later, Alexander Bryson proved the value of careful epidemiological data collection and observation of infectious diseases encountered on the West Africa station. In the 20th century, Royal Navy physicians were at the cutting edge of vaccine research and antibiotic production. Nuclear submarines placed naval physicians at the forefront of nuclear medicine and environmental safety. The development of new aircraft carriers has driven a renewed interest in aviation medicine. This article reviews the contributions that Royal Navy physicians have made to medicine over the centuries, detailing some of the better known as well as some almost forgotten, but still remarkable, achievements.