The Gulf of Papua is a 400 kilometer wide region on the south shore of New Guinea

New Guinea

New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

. Some of New Guinea's largest rivers, such as the Fly River

Fly River

The Fly at , is the second longest river, after the Sepik, in Papua New Guinea. The Fly is the largest river in Oceania, the largest in the world without a single dam in its catchment, and overall ranks as the twenty-fifth largest river in the world by volume of discharge...

, Turama River

Turama River

-See also:*List of rivers of Oceania...

, Kikori River

Kikori River

The Kikori River is a river in southern Papua New Guinea on the island of New Guinea .The river is about long and flows southeast into the Gulf of Papua, with its delta at the head of the gulf. The settlement of Kikori lies on the delta.-References:...

 and Purari River

Purari River

The Purari is a river in that originates in the south central highlands of Papua New Guinea, flowing though the Gulf Province to the Gulf of Papua...

, flow into the gulf, making it a large delta. While the western coast is characterized by swamp

Swamp

A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or swamp...

y tidal waterways, land to the east ending at Cape Possession

Cape Possession

Cape Possession is a cape which forms the west extremity of Chanticleer Island, just west of Hoseason Island in the Palmer Archipelago. The name was applied by Captain Henry Foster of the Chanticleer, whose party made a landing in this vicinity on January 7, 1829....

 is flat and sandy. The Papuan Gulf's central and eastern interior slowly rises to meet the mountainous Southern Highlands, and is covered in a variety of inland swamps and dense tropical hardwood forests.