Which marginal sea is the deepest in the world?

The Philippine Sea is the deepest marginal sea in the world.

It is a marginal sea of the western Pacific, east of the Philippine Archipelago and west of the Mariana Islands. Its floor is shaped by active plate boundaries, island arcs and deep trenches, including the Philippine Trench and the Mariana Trench.

The Mariana Trench contains Challenger Deep, the deepest known point on Earth, at nearly 11,000 metres below sea level. That extreme depth is why the Philippine Sea is deeper than alternatives such as the Bering, Tasman and Coral seas. Depth figures can vary slightly with surveying methods and definitions of the sea’s boundaries.

The Philippine Sea is also among the world’s largest seas by area and supports rich marine ecosystems. It should not be confused with the West Philippine Sea, a Philippine government term for parts of the South China Sea, west of the archipelago.