If rescue crews do manage to locate the missing submarine thousands of feet below sea level, they face a series of barriers and an incredibly complex mission to retrieve the vessel.
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BBC News
By Michael Dempsey
image captionThe naming ceremony of HMS Anson in Barrow-in-Furness
On 20 April, the Royal Navy s latest nuclear-powered hunter-killer submarine, HMS Anson, emerged from a vast construction hall at Barrow-in-Furness, travelled down a slipway and entered the water. All 7,400 tonnes of it.
Around 260 miles away in Plymouth, another submarine made its debut that same day. A minnow compared to HMS Anson, this secretive nine-tonne craft may have greater implications for the future of the navy than the £1.3bn nuclear boat.
MSubs of Plymouth, a specialist in autonomous underwater vehicles, won a £2.5m Ministry of Defence contract to build and test an Extra-Large Unmanned Underwater Vehicle (XLUUV) that should be able to operate up to 3,000 miles from home for three months.
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