Due to the randomness of where treasure will spawn, it can occasionally spawn inside of map pieces.
In this video, one of the treasure spots was inside one of the train supports.
(I will note that at the time of the video, I had collected all of the other treasures, so this was not a case of two nearby treasures confusing the metal detector)
Before this I also had one spawn beneath the life guard shack, which I was fortunately able to reach by crouching (presumably a tiny potion would also work), but it puts into question the possibility of spawning in an unreachable spot there.
