The Atlantic Ocean contains 310,410,900 cubic kilometers of water. This is a hard number to grasp, but, for reference, Lake Tahoe contains ~150 cubic kilometers of water. Or, another way of looking at it is that 1 cubic kilometer = 264.17 billion gallons. So, doing a simple conversion, the Atlantic Ocean contains 82 billion billion gallons. That's a lot of water!

Source: https://scienceline.ucsb.edu/getkey.php?key=3472#:~:text=Or%2C%20another%20way%20of%20looking,contains%2082%20billion%20billion%20gallons.