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The Lombok Strait
The deep Indonesian channel between Bali and Lombok that takes supertankers too deep-laden for the Strait of Malacca
When a fully laden supertanker from the Persian Gulf is too deep for the Strait of Malacca, it often heads for the Lombok Strait instead. This channel between the Indonesian islands of Bali and Lombok is at least 250 meters deep, enough for the largest ships afloat, and it links the Indian Ocean with the Bali Sea and, beyond it, the Makassar Strait route north to China, Japan and Korea. It is also a dividing line in the natural world. The naturalist Alfred Russel Wallace noticed in 1856 that the birds of Bali and Lombok belonged to strikingly different faunas, and the boundary he described between Asian and Australasian wildlife still bears his name.
The strait runs about 60 kilometers north to south between Bali on the west and Lombok on the east. It is about 40 kilometers wide at its northern entrance and narrows to roughly 20 kilometers at the southern opening, where the island of Nusa Penida lies off Bali. Depths of 250 meters or more let deep-draft vessels pass, unlike the Strait of Malacca, whose shallowest stretches limit the most heavily laden ships to roughly 20 to 25 meters of draft. A strong southward current, part of the Indonesian Throughflow that carries Pacific water into the Indian Ocean, runs through it, and large internal waves form over its southern sill. Since July 2020 shipping has followed an IMO traffic separation scheme, and the strait forms part of Indonesia's second archipelagic sea lane, which continues north through the Makassar Strait.
The deep water here has kept the islands apart for millions of years, even when Ice Age sea levels fell far enough to join Bali to Java and mainland Asia. That is why tigers once lived on Bali while cockatoos and other Australasian species occur on Lombok, a contrast that helped Wallace develop his ideas on evolution and the geography of species. For shipping the strait's value is depth and an uncrowded route. Indonesia promotes it as an alternative to the busy Strait of Malacca, and very large crude carriers and ore carriers bound for northeast Asia use it. The strait lies within Indonesia's archipelagic waters, where foreign ships hold the right of archipelagic sea-lanes passage under the UN Convention on the Law of the Sea. Ferries and fast boats cross it daily between Bali, the Gili Islands and Lombok.