Saltwater Crocodiles “Surf” Ocean Currents Across the Indo-Pacific

Saltwater crocodiles are extraordinary animals. As the largest reptiles on Earth, they possess a bite force of about 3,700 PSI—far exceeding that of humans. Yet despite their size and power, they are surprisingly poor long-distance swimmers. Even so, these reptiles have managed to spread across vast areas of the Indo-Pacific, leaving scientists puzzled about how they accomplished such journeys.

Saltwater crocodiles typically inhabit estuaries, mangrove swamps, deltas, and floodplains, and they can survive in fresh, brackish, or saltwater. Their range stretches from India and the Philippines through Papua New Guinea to northern Australia—distances that seem far beyond what their swimming ability should allow.

Researchers investigating this mystery uncovered an unexpected explanation: saltwater crocodiles use ocean currents to travel long distances, effectively “surfing” the sea.

In a 2010 study, scientists fitted 27 adult crocodiles in Australia’s Kennedy River with sonar transmitters and tracked their movements for a year. The data revealed a clear pattern. The crocodiles began long journeys shortly after tides changed, allowing currents to carry them. When the currents weakened, the animals would rest on riverbanks or coastlines, resuming travel only when conditions became favorable again.

Some tagged crocodiles covered more than 30 miles using this method. They swam short distances—around six miles at a time—while currents assisted them, resting between movements. Similar behavior was observed among crocodiles traveling in open ocean waters.

According to study author Dr. Hamish Campbell of the University of Queensland, this strategy explains how saltwater crocodiles maintain populations across islands throughout the Indian and Pacific oceans. “These crocodiles are poor swimmers and unlikely to cross vast stretches of ocean on their own,” he explained. “But they can survive long periods in saltwater without eating or drinking. By moving only when surface currents are favorable, they can travel great distances by sea.”

The discovery provided a breakthrough in understanding crocodile migration. Researchers concluded that this current-assisted travel not only explains how modern saltwater crocodiles move between islands, but also supports the idea that crocodilian species crossed major ocean barriers during their evolutionary history.