"Much of the deep sea has never been explored close-up by humans. Some submarines have plumbed its depths, but reaching the ocean bottom is a complicated and expensive journey, challenging because the seabed lies under more than three miles of water, which exerts huge amounts of pressure. “We know more about space than about the bottom of the oceans in our own planet, even though more than two-thirds of the surface of the Earth is covered by marine sediments,” said Olivier Sulpis, a researcher and doctoral student at McGill University’s department of earth and planetary sciences."

https://www.popsci.com/seafloor-disappearing-acidification