(IDEX Online) - The world's most advanced diamond recovery vessel, the $420m Benguela Gem, is to set sail off the coast of Namibia next week.The 177-meter ship (pictured) will join Debmarine's existing five-strong fleet, which dredge thousands of tonnes of sediment fat 90 to 150 meters below the seabed, 12 miles off the south-western coast. It is expected to increase Debmarine's output by about 500,000 carats.The ship was designed in Norway and Poland, built in Romania and fitted out with its proprietary mission equipment by De Beers Marine South Africa. Debmarine, a 50/50 joint venture between De Beers Group and the Government of the Republic of Namibia, produces 1.4m carats annually. Bruce Cleaver, CEO, De Beers Group, said: "The Benguela Gem is the first of its kind and represents an outstanding feat of engineering design, technology innovation and sustainability performance."Despite significant challenges presented by Covid-19, the project was delivered ahead of time and budget - a testament to the world-leading skill and expertise of all involved."It uses either airlift-drill technology, or on more modern ships, a 280-tonne track-mounted remote-controled crawler to bring up the gravel. Then they wash, sift and sort it on board, and return the sediment - as well as the odd octopus - back to the bottom of the ocean.The diamonds are automatically sealed into barcoded steel briefcases and flown by helicopter three times a week to vaults back on dry land, in the capital Windhoek to be graded.