In 2001 a remotely operated vehicle in the Gulf of Mexico captured footage of either a Greenland shark or a sleeper shark in over 2,600 metres of water.
Two years later, scientists from the Harbour Branch Oceanographic Institution in Fort Pierce, Florida, became the first people to come face to face with a Greenland shark in the deep sea.
The shark, which was 16-feet-long, bumped into their submersible vessel 1,000 metres down in the Gulf of Maine.
But hardly anyone dives that deep, so these rare encounters reveal little about how widespread and important the Greenland sharks are.
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