This 4 October 2018 video says about itself:
Girl, 8, pulls a 1,500-year-old sword from a lake in Sweden.
It reminds me a bit of a Vietnamese legend; from Wikipedia:
According to the legend, in early 1428, Emperor Lê Lợi was boating on the lake when a Golden Turtle God (Kim Qui) surfaced and asked for his magic sword, Heaven’s Will. Lợi concluded that Kim Qui had come to reclaim the sword that its master, a local God, the Dragon King (Long Vương) had given Lợi some time earlier, during his revolt against Ming China. Later, Emperor Lợi gave the sword back to the turtle after he finished fighting off the Chinese. Emperor Lợi renamed the lake to commemorate this event, from its former name Luc Thuy meaning “Green Water”.
In medieval British Arthurian legends, King Arthur obtained his sword Excalibur from the water, given by the Lady of the Lake.
Translated from Dutch NOS TV today:
Girl (8) pulls 1500-years-old sword from lake
An 8-year-old girl has, in Sweden, recovered a 1500-year-old sword from a lake. While swimming on holiday in Jönköping, Saga Vanecek took the 85-centimeter weapon out of the mud.
“I felt something in the water and pulled it up. When I saw a handle, I told my father it looked like a sword”, Saga told the Swedish media. The find was extra special for the Swedish-American girl because she is a fan of the Vikings NFL [American football] team.
Her father initially thought that Saga had “found an unusual stick”, but further research soon indicated that it was a special archaeological find. According to experts, the weapon is very well preserved. Thus the sheath of leather and wood is still around the blade.
According to the local museum, the discovery was possible because the water in the lake was exceptionally low this summer due to the drought. Furthermore, it is being investigated whether more finds can be made. A brooch from the Iron Age has already been found.
Archaeologists have no idea how the sword landed in the water. It may have been thrown into the lake as an offering or simply lost, but it is also possible that it has been washed away from a grave.