These hair-raising pictures show brave tourists risking their lives for pictures as they strayed close to fighting jaguars.
Seasoned wildlife photographer Paul Williams was overjoyed to finally find elusive jaguars in their natural habitat, the Brazilian Pantanal, the world's largest tropical wetland area.
But Paul, 34, who works for the BBC Natural History Unit, soon found his joy turn to terror as he watched foolhardy tour boats jostling to see which could get the closest.
He had planned to film the amazing scenes, but was quickly blocked by several tourist boats wanting to get the best view.
Paul told Rex Features: "I came across this group of young males on the corner of a river in the northern Pantanal - they appeared to be play-fighting. It wasn't long before a group of tourist boats also spotted the scene but I kept my distance knowing how dangerous jaguar are.
"The tourists went far too close for comfort. These cats have powerful legs and can jump several metres in one bound. In fact their name comes from the native American word yaguar meaning 'he who kills in one leap'.
"At the time we guessed that they were about five metres away just of the edge of the bank.
"I couldn't believe my luck when we stumbled across a scene of four jaguar on a bend in the river (we only ever got a shot of 3 in the same frame) - a female and three large, but immature, males. We assumed that they were closely related and this would be a unique opportunity to film and photograph natural behaviour.
"I was guided by Mr Toto, who grew up navigating the waterways of the Pantanal. His philosophy is very much the same as ours - to observe natural behaviour and not to influence it. So we did the safest and least intrusive thing we could and moved our boat to the opposite bank where we could use our long lens to capture the action from a safe distance.
"Unfortunately less than 10 minutes later several boats sped into the scene, straight in front of us, blocking our view and putting themselves directly in the line of danger. As the numbers of boats increased the drivers became more aggressive towards one another, cutting each other up to get closer and closer until they were too close for comfort.
"The cats were clearly disturbed by this and didn't stay around long - but had they been so inclined it would have been easy for one of the jaguar to run and leap straight into a boat.
"This area is officially protected but it is down to common courtesy and an unwritten code between guides. Mr Toto said that many of these boat drivers had no training in good practice and did not realise, or care about how their behaviour influenced the animals.
"Sadly it's a scene that's too common in natural parks around the world, but it's important to remember that without tourism many of these areas would be under threat. Everyone has the right to experience nature and wildlife, but the organisations and companies who manage this have a responsibility to ensure that the welfare of the wildlife is paramount."
Paul counted himself lucky on the trip, having had "7 stunning jaguar sightings in 3 days", although he describes the experience as having an unsettling aspect.
"I had been following an otter along a river in the northern Pantanal when I looked up and saw the transfixed eyes of a jaguar staring out from the shade. It's one of the few times that I've looked an animal in the eye knowing that I was the prey," he says.
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