The underwater topography of the shelf that forms the seabed is a plain, sloping from southwest to northeast, covered in a mixture of silt, sand and stones and lacking significant depressions and elevations. About 70% of the sea is shallower than 50 m, with predominant depths of 20–25 m. North-east to the mouth of the Kolyma and Indigirka rivers, there are deep trenches on the seabed, which are attributed to the ancient river valleys, now submerged by the sea. The region of small depths in the western part forms the Novosibirsk shoal. The greatest depths of about 150 m are found in the north-eastern part of the sea.