When Sylvester Stallone was making Rocky III, he need a monster villain to fight. He found one not in the world of boxing or even in Hollywood but in the wrestling ring. The 6ft 7in, 300lb Hulk Hogan.

Unseen, largely unknown and, until recently, highly classified, the US Navy’s vast network of underwater sonars is one of its greatest advantages over rival fleets. The United States can detect many, ...