Johnny Hartnell, 49, has been swimming in the natural pool beneath Janet's Foss since he was a child, but cannot remember the well-known waterfall near Malham Cove ever drying up before.
When he arrived for an early morning dip earlier this week, the waterfall was a trickle and the crystal-clear pool was all but empty.
There were just a couple of inches of water left in a corner where brown trout and bullhead fish were frantically flapping in a bid to stay alive.
"I've been swimming at Janet's Foss for years and I've never seen anything like it. It was shocking," said Johnny, from Ingleton.
"There was no rain forecast so it was only going to get worse. I just thought, 'I've shared that pool with the fish on many occasions and I've enjoyed watching them. I must do something.'"
He headed home to fetch a landing net and a bucket before driving back to Malham, where he was joined in the recuse effort by local farmer Malcolm Wilson.
"I flagged him down to ask if there was another pool that I could get the fish to and he came to help me. He was fantastic and we spent about an hour and a half scooping the fish out. By that point the water level had dropped by another inch."
The pair managed to rescue about 30 brown trout and 100 bullheads. Using Malcolm's local knowledge, they released them in another natural pool upstream. Fish weren't the only things they found in the mud.
"There was all sorts from a pair of sunglasses to a watch that was still working. We also found a stone that read 'Diane RIP'," says Johnny, who works at the Inglesport outdoor shop in Ingleton.
He is looking forward to returning to Janet's Foss when rainfall has replenished it.
"I am an avid wild swimmer and it is my favourite place to take a dip. It's about 10ft deep and it's gin clear so you can see the trout beneath you."
There may also be fairies. According to legend, the cave behind the falls is said to be home to Jennet, queen of the fairies, hence its name "Janet's Foss". There is certainly something magical about it. The falls and the pool beneath are set in a stunningly beautiful woodland, which is alive with birdsong and covered with carpets of bluebells and flowering wild garlic in the spring. The lime-rich water has deposited a screen of moss-covered tufa underneath the waterfall. This porous rock formed from calcium carbonate and topped with a rich green coat adds to the ethereal effect of the scene.
Now owned by the National Trust, Janet's Foss is a popular destination for walkers who make the pilgrimage from the nearby village of Malham. While many will be disappointed to find it dried up due to the heatwave, cooler weather with some rain is forecast.
The prolonged period of warm weather has also seen other watercourses in Yorkshire run dry, including the River Wharfe at High Raisgill in Upper Wharfedale.