The Timor Sea marks the eastward boundary of the central Indian Ocean. Pacific water flows in from the Arafura Sea during the southwest monsoon, feeding the South Equatorial Current. This flow is reversed during the northeast monsoon. Australia’s aboriginal people probably arrived from southeast Asia by island-hopping across the Timor Sea. It is mainly shallow, but with the deep Timor Trough lying along its northern edge. Significant reserves of oil and gas are thought to lie in the continental shelf sediments beneath the sea, and exploitation rights are disputed between Australia and East Timor. The warm shallow tropical waters make the Timor Sea a breeding ground for tropical storms and cyclones from January to March. Such storms proceed southwestward into the Indian Ocean, sometimes turning inland to hit the coast of Western Australia. There are fishing grounds, including a shrimp fishery, in coastal waters on the Australian side of the Timor Sea.