The planet’s oceans might cover more than 70% of its surface, but they still remain mostly unexplored by humans.
Although a substantial number of sea creatures living in the depths of the seas has been discovered in recent years, scientists estimate that the species that remain a mystery still outweigh those for which they have collected data.
From enormous cephalopods (octopuses, squid) to sea-giants of the depths (whale sharks, whales) and from the humongous Japanese crabs to poisonous jellyfish with tentacles up to 5 meters long, the abyss of the sea remains a well-hidden mystery, even for those who have spent their entire life exploring it.

Science Insider presents the most terrifying sea creatures you might come across several kilometres below the sea level.