THE NETS enclosing the inner harbour draw open. A black-finned predator slips out. Minutes later it reaches the open ocean and, with a great exhalation, disappears beneath the tropical waters. Getting under way from Apra Harbour in Guam, the USS Annapolis, one of the ocean’s apex hunters, is engaged in a silent but intensifying contest with China and Russia for dominance of the vast Pacific.Photograph: U.S. Naval Forces Europe-Africa/U.S. Sixth FleetWarships are noisy, rumbling along like lorries. Not so a nuclear-powered attack submarine, which hums like a Tesla. For months on end the Annapolis’s crew of 145 men (and, when...