This heron was in for a shock when the 'rock' it was perched on to fish from turned out to be a hippo.
The bird realised something strange was going on in Kruger National Park, South Africa, after the spot it had landed on suddenly began to move.
However, undeterred from its task, the clever heron continued to use the unsuspecting mammal as the perfect hunting platform.
During the remarkable 10-minute encounter the heron desperately tried to keep balance as the hippo repeatedly came up for air.
Finally, it managed to spot a frog in the water, which it skilfully picked up in its beak before flying off with its catch.
At first, British photographer Andrew Forsyth thought the heron was sitting on top of a small mud island.
It was only when the huge creature emerged from the water that he realised it was a hippo wallowing in a mud bath.
The 42-year-old from Brighton, East Sussex, said: 'The scene was already quite special because there was an orange haze caused by bush fires that raged in the distance as the sun went down.
'I spotted the heron on what I thought was a small mud island and watched it as it looked for fish for several minutes.
'Suddenly the "island" rose up out of the water, two nostrils appeared and took a big breath then went under again.
'I watched it for several minutes, again with the heron looking out for fish passing by, the hippo rising and falling occasionally as he breathed.
'The hippo didn't seem to mind the presence of the passenger - I do wonder if it felt like a good back scratch for him.'
Mr Forsyth continued: 'The hippo rose and sank a few times more and the heron stayed put stubbornly refusing to be offloaded, despite a few balancing problems which were corrected by opening his wings.
'At last the hippo had enough and rose high out of the water, turned and walked towards a shallow section of the lake, the heron appearing to surf on his back as he went.
'As he sank down below the water again he obviously disturbed a frog, the heron seized his chance to grab a quick meal and flew off with the prize.
'The fact that such a large animal is also likely to disturb fish and amphibians hiding in the bed of the lake is probably a bonus for him, one that paid off here.'
The photographer added: 'I've made several trips to Kruger and not seen behaviour like this before or since, so I feel privileged to have seen this interaction between a hunter and another animal that inadvertently helps him catch his prey.'