The bay is open to the north and is 140 km in length. Its maximum width is 110 km.[1] Its mouth is defined by Cape Shelagsky, the end of the Shelag Range, to the east and an unnamed part of Ayon Island to the west. It narrows where the Pevek Peninsula on the east approaches Ayon Island.
Owing to is northerly location Chaunskaya Bay is covered with ice most of the year.