1 Monty: Sallah's on his way. Though he pointed out that according to the legends Excalibur was returned to the Lady of the Lake.
2 Prof. Jones: Oh well obviously, everyone knows what the legends say. You don't trust those, do you?
3 Monty: I don't even trust that the sword exists!
4 Prof. Jones: Well there you go. It can't be at the bottom of a lake then, can it?

Finding Excalibur these days should be no more difficult than finding the Lake where the Lady lived, and draining it so you can dredge the bottom. The main problem^[1] is nobody can agree in exactly which lake is the correct one. Wikipedia's Lady of the Lake article lists as many as ten different purported locations for the lake.

I suppose we could just go and drain every lake in England and Wales until we found a cool sword. Actually, I bet if you did that, the odds are you'd find several swords. Then you'd have the problem of figuring out which is the right one!

[1] Besides it being, like, probably, a myth.