where does the coral sea end and pacific ocean start?

Answer 1

I think technically the Coral Sea is part of the Pacific Ocean. See #2 for details of its location.

"The Coral Sea is a region of the north-east coast of Australia with a namesake chain of islands (uninhabited), including the Willis, Coringa, and Tregosse Islets. The Coral Sea is named for its primary feature, the Great Barrier Reef, which is the largest coral reef in the world. The territory is a possession of Australia, administered from Canberra by the Australian Department of the Environment." [1]

"[It is a] sea of the southwestern Pacific Ocean, extending east of Australia and New Guinea, west of New Caledonia and the New Hebrides, and south of the Solomon Islands. It is about 1,400 miles (2,250 km) north-south and 1,500 miles east-west and covers an area of 1,849,800 square miles (4,791,000 square km). To the south it merges with the Tasman Sea, to the north with the Solomon Sea, and to the east with the Pacific;" [2]

"Pacific Ocean: body of water between the Southern Ocean, Asia, Australia, and the Western Hemisphere with a total area of 155.557 million sq km including Bali Sea, Bering Sea, Bering Strait, Coral Sea, East China Sea, Gulf of Alaska, Gulf of Tonkin, Philippine Sea, Sea of Japan, Sea of Okhotsk, South China Sea, Tasman Sea, and other tributary water bodies" [3]