Matilda Jones, aged seven, from Doncaster, found the sword when she was paddling in Dozmary Pool, in Cornwall with her dad, Paul.
Paul, aged 51, had told Matilda and her sister Lois, four, about the legend of King Arthur on their journey to the lake.
He said: “It was a blistering hot day and Matilda asked if we could go for a paddle. She was only waist deep when she said she could see a sword.
“I told her not to be silly and it was probably a bit of fencing, but when I looked down I realised it was a sword. It was just there laying flat on the bottom of the lake.”
Folklore has it that Dozmary Pool is said to be where Excalibur was thrown by Sir Bedivere after the Battle of Camlann and Arthur’s death.
According to local tradition after three attempts to relinquish the sword, Sir Bedivere finally managed to comply with King Arthur’s wish and threw it into the lake, an arm rose from the surface, caught the sword and vanished back into the water.
It is also the home of the Lady of the Lake and is where a young Arthur rowed out to claim the mighty Excalibur.
After arriving Paul and Matilda went for a paddle in the lake and the child made the discovery on Tuesday, August 29.
“The sword is 4ft long – exactly Matilda’s height,” added Paul. “I don’t think it’s particularly old about 20 or 30 years old. It’s probably an old film prop.”
At the end of their six-day holiday the family brought the sword home and Matilda and Lois are enjoying telling all her family and friends about her discovery.
This article first appeared at our sister site, the Sheffield Star.