The enormous elephants gently skim the pool with the tips of their trunks to get to the clean water
Cameras have revealed how elephants are able to get a drink of fresh water when faced with a stagnant waterhole.
A BBC team discovered that the tusked giants use their trunks to delicately siphon off clean liquid that has settled at the top of the dirty pool.
The footage shows how the elephants move incredibly slowly to avoid stirring up any sediment.
The Natural History Unit team said this was the first time that they had seen this resourceful behaviour.
However much we think we know about elephants, they always surprise us with some new and intelligent piece of behaviour
The film forms part of Nature's Great Events: The Great Flood, which follows the annual flooding of Botswana's Okavango Delta, where, for a limited time, the surrounding desert is transformed into a lush wetland.
The new behaviour was recorded in the Kalahari Desert just before the arrival of the flood; temperatures during the dry season can soar above 50C.
The BBC team waited by a waterhole - a lifeline for animals living on this parched terrain - to film the elephants as they came to drink.
The Okavango Delta floods each year
Wildlife cameraman Mike Holding said: "Thirsty elephants usually rush head-long into water and splash with abandon, but this group did something I had never seen before - they approached the pool quietly and stepped in very slowly, making as little disturbance as possible.
"And then, remarkably, one after another, the elephants began to carefully sweep their trunk tips across the surface, delicately siphoning the few centimetres of clear liquid from the mud below."
The film-maker says he has never seen the elephants use their trunks in this way before.
He said: "I have spent countless days in the company of elephants, and I believe this was a timely reminder that however much we think we know about elephants, they always surprise us with some new and intelligent piece of behaviour."
Nature's Great Events: The Great Flood is on Wednesday 11 March on BBC One at 2100 GMT and is repeated on Sunday at 1800 GMT
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