Submarine Alvin
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US manned deep-submersible Alvin prepares to resume work

The tiny three-man submarine Alvin has been the workhorse of ocean research for nearly 50 years - finding new life forms and advancing understanding of the underwater world.

It is nearing the end of a $41m refit and is about to embark on a series of engineering test dives before returning to the ocean for research duties in May.

The BBC's Pallab Ghosh was given a sneak preview.

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