World
Oceans
The seas that cover most of the planet: their depths, currents, tides and colour, and the dives and voyages that measured them.
Fact files
All topics ›The seafloor
28.7 %
Ocean floor mapped at high resolution, as of April 2026
Seawater
97 %
Share of Earth's water held in the ocean
Ocean tides
2
High tides in a lunar day on most coasts
The mid-ocean ridge
65,000 km
Length of the ridge system, NOAA figure
The Challenger Deep
10,935 metres
Depth of the Challenger Deep, NOAA figure
The five oceans
71 percent
Share of Earth's surface covered by the ocean
The Mediterranean Sea
5.96 to 5.33 million years ago
Span of the Messinian salinity crisis, 2011 study
The Pacific Ocean
155 million square kilometres
Area of the Pacific Ocean
The Great Barrier Reef
348,000 square kilometres
Area of the World Heritage property
The Titanic
2,223 people
Aboard, per the US National Archives