Ocean water is approximately 3.8 billion years old.
Over a vast period of time, the Earth's primitive ocean formed. Water existed as a gas until the planet cooled below 212 degrees Fahrenheit (100 degrees Celsius). Around 3.8 billion years ago, this water condensed into rain, which then filled the basins that would become our world ocean.
Therefore, while water continues to cycle through the ocean, the origin of the water that makes up the ocean dates back nearly 4 billion years.
