Deepest dive by a sea snake
Hydrophis sea snake
245 metre(s)
Australia ()

On 16 November 2014, a Hydrophis sea snake (species undetermined) was captured on video swimming at a depth of 245 metres (803 feet 9 inches) by a remotely operated vehicle (ROV) in the Browse Basin, which lies off north-west Australia, as described in Austral Ecology on 18 March 2019. Proving that this wasn’t a one-off, a subsequent ROV recorded another Hydrophis sea snake in the same location on 18 July 2017 at a depth of 239 metres (784 feet 1 inch), seemingly foraging on the sandy seabed

Until this point, reports of sea snakes at greater depths than 100 metres (328 feet) have been few and far between. In 1993, an olive sea snake (Aipysurus laevis) was witnessed by a diver at 133 metres (436 feet 4 inches) at the Goodwin oil platform on the North West Shelf off Western Australia.

As well as an unprecedented depth for a sea snake, this also challenges current thinking around sea snakes’ thermal tolerance. The ROV recorded a temperature of 14.5°C (58.1°F) during the 2017 sighting, which questions the notion that sea snakes cease to be active under 18°C (64.4°F).

Physiological features that allow for sea snakes to endure the conditions at such depths need further study, but are likely to include a more efficient subcutaneous gas exchange than previously realized, preventing these reptiles from experiencing “the bends”.

The research was conducted by the University of Adelaide, James Cook University, the Australian Institute of Marine Science, ROV operator INPEX (all Australia) and The Royal Danish Academy of Fine Arts, School of Architecture, Design and Conservation (Denmark), with their findings published in the journal Austral Ecology on 18 March 2019.