Tiny gap in the ocean could become the world’s most expensive tollbooth

Iran's attempts to exact a hefty toll on ships passing through the Strait of Hormuz has given other countries an idea.

Senior politicians in both Malaysia and Indonesia have floated the idea of exacting a toll on one of the most important waterways on Earth – the Strait of Malacca.

"We sit on a strategic global trade and energy route, yet ships pass through the Malacca Strait without being charged – I'm not sure whether that's right or wrong," Indonesia's Finance Minister Purbaya Yudhi Sadewa said last month.

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Malaysian Foreign Minister Sugiono responded by saying Indonesia could not impose a toll on ships without them.

"Whatever is to be done in the Strait of Malacca must involve the cooperation of all four countries," he said.

"That is our understanding – it cannot be done unilaterally."

The four countries Sugiono is speaking of are Singapore, Malaysia, Indonesia and Thailand.

An immense number of ships pass through the narrow waters between those four countries.

If a million-dollar per ship toll were exacted, it would be a $100 billion annual windfall for the countries involved.

"It's the only reasonable route from East Asia to Europe or the East Coast US," University of Sydney's Professor of Ports and Maritime Logistics Michael Bell said.

"The only other alternative is going all the way around Australia."

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Much of Australian petrol is refined in Singapore from oil brought through the Strait of Malacca.

While there are countless gaps between islands in Indonesia, they are too shallow and difficult to traverse for major vessels.

At its narrowest, the Strait of Malacca was just 2.8km across.

"There's definitely a bottleneck that you could charge ships for going through," Bell said.

Passing through the Strait is nearly half of all seaborne oil in the world, including much that winds up in Australian cars.

A quarter of cars and nearly a quarter of dry bulk cargo also goes through the Strait.

But a toll on the Strait of Malacca isn't likely, according to Adjunct Fellow in Naval Studies at University of NSW Jennifer Parker.

"It will not happen," she said.

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An immense amount of shipping goes through the strait every day.

"If Malaysia, Singapore and Indonesia agreed that they would apply some sort of toll on the Malacca Strait, which is an international strait, then that would be undermining the UN Convention of the Law of the Sea."

But trying to enforce a toll on the strait would put them in an awkward position with China.

"These countries value their relationships with the international system a lot more than Iran seems to do," Parker said.

"They also value their economic relationships with China."

Much of China's global trade is dependent on access to the strait, and the superpower in the region retains a lot of clout.

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At its narrowest, the Strait of Malacca is just 2.8km wide.

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