Blue Water was a British battlefield nuclear missile of the early 1960s, intended to replace the MGM-5 Corporal, which was becoming obsolete. With roughly the same role and range as Corporal, Blue Water was a far simpler missile that was significantly easier to support in the field. It was seen as a replacement for Corporal both in the UK as well as other NATO operators, notably Germany and possibly Turkey.
The missile entered testing in 1962 was generally successful, and praised in the industry. However, when Germany purchased the MGM-29 Sergeant instead of Blue Water, and it appeared Turkey would do the same, the UK government decided to cancel its development instead of continuing to develop a missile that would be used only by their own forces.
Blue Water was a code name assigned randomly by the Ministry of Supply based on their Rainbow Code system. It was also known as Red Rose early in development.
In 1956 the Corporal missile had been adopted by the Royal Artillery as a battlefield tactical nuclear missile. This missile was liquid-fuelled, thus requiring a large convoy of support vehicles to prepare it slowly for launch. It also required continual command guidance in flight, yet only achieved relatively poor accuracy. Also in use within the Royal Artillery was the Honest John rocket. This was solid-fuelled and could be launched rapidly, but was unguided and had only short range. There was a clear requirement for a missile that would combine guidance and long range with rapid deployment and easy operation.
This resulted in a 1958 Operational Requirement for a "short-range corps support weapon" that was solid-fuelled with autonomous guidance and requiring only simple support equipment for launch. It also took advantage of the shrinking dimensions and weight of nuclear warheads and so only required a much smaller payload. It was also a requirement that the system should be air-portable through the RAF's standard Argosy transport aircraft. Like the Corporal, range was set at around 55 miles (89 km).