From the Red Sea to the Andaman: Seas and Gulfs of the Northern Indian Ocean

The starting point. A narrow inlet between the Arabian Peninsula and northeastern Africa, covering about 438,000 square kilometres. It reaches the ocean in the south through the Bab-el-Mandeb strait and the Gulf of Aden, and the Suez Canal links it to the Mediterranean. It is among the saltiest and warmest bodies of seawater in the world and supports extensive coral reefs.

The northwestern arm of the Red Sea, about 300 kilometres long and up to 70 metres deep, separating the Sinai Peninsula from mainland Egypt. It leads north to the Suez Canal, so tanker traffic bound for the canal passes through it, and it holds significant offshore oil fields.

The northeastern arm of the Red Sea, about 160 kilometres long, with a surface area of 3,680 square kilometres. Despite its small size it reaches a maximum depth of 1,850 metres. Egypt, Israel, Jordan and Saudi Arabia border it, and it gives Jordan and Israel their only direct sea access to the Red Sea and Indian Ocean.

Leaving the Red Sea through the Bab-el-Mandeb strait, the route enters this gulf between Yemen and Somalia. It covers about 410,000 square kilometres and is up to 2,700 metres deep. It sits astride one of the world's busiest shipping lanes and has been a focus of international anti-piracy patrols.

The gulf opens into the northern Indian Ocean here. The Arabian Sea is bounded by the Arabian Peninsula, Iran, Pakistan and India, and is far larger than anything so far on the path at 3,862,000 square kilometres, with a maximum depth of 5,395 metres. Strong seasonal monsoon winds drive its currents and have shaped trade and navigation across it for millennia.

Bordered by Oman, Iran and the United Arab Emirates, about 115,000 square kilometres and up to 3,700 metres deep. It links the Arabian Sea to the Strait of Hormuz and, beyond it, the Persian Gulf, and much of the world's seaborne oil exports pass through its waters.

Through the Strait of Hormuz lies the Persian Gulf, an extension of the Arabian Sea between the Arabian Peninsula and Iran. It is 989 kilometres long and covers 251,000 square kilometres, yet is shallow, reaching only about 90 metres. The Shatt al-Arab river delta forms its northwest shoreline, and it is also called the Arabian Gulf.

The path now turns east. The Bay of Bengal is the largest bay in the world, about 2,090 kilometres long and 2,600,000 square kilometres in area, reaching 4,694 metres deep. It receives the combined outflow of the Ganges and Brahmaputra rivers and is prone to some of the deadliest tropical cyclones on record.

The end of the path. This marginal sea lies between the Andaman and Nicobar Islands and the coasts of Myanmar, Thailand and Malaysia, about 797,000 square kilometres and up to 4,198 metres deep. Its waters were severely affected by the 2004 Indian Ocean tsunami, generated by an undersea earthquake near Sumatra.