How deep are the oceans and seas
This reference lists the five oceans and more than twenty major seas, ranked by maximum depth. For each it shows the average depth, the maximum sounded depth in metres, and the name of the deepest point — usually an ocean trench. Switch between oceans, seas, or both, and filter by any name or feature.
How it works
Two very different numbers describe a body of water’s depth. The average depth is the total water volume divided by the surface area: it tells you how deep the basin is on the whole. The maximum depth is the deepest single point ever measured, almost always inside a subduction trench where one tectonic plate dives beneath another.
The gap between the two can be enormous. The Pacific averages about 4,280 m but plunges to roughly 10,935 m at the Challenger Deep. Marginal seas perched on continental shelves — the North Sea, Baltic and Yellow Sea — stay shallow throughout, while seas over active plate boundaries, like the Philippine and Caribbean, reach trench depths rivalling the open ocean.
Notes and caveats
- The Southern Ocean’s boundary (the waters around Antarctica) is defined by the Antarctic Circumpolar Current; not all authorities recognise it as separate.
- Maximum-depth figures are refined as multibeam sonar surveys improve, so exact values shift slightly between sources.
- Average depths reflect basin shape: a few deep trenches barely move the average if most of the basin is shallower.
- All depths are below mean sea level, in metres.