The Legend of Zelda: Breath of the Wild isn't short of mysteries. With hundreds of sidequests to complete and Korok Seeds to uncover, you'll be playing Link's latest adventure for a long time before you've seen it all. But there's one mystery that remained unsolvable due to what one can only assume is a glitch in the game.
Buried in a small inlet between the Clarnet Coast and Aris Beach lies a buried treasure chest. Ordinarily, Link can snag these out of the ground with his magnesis ability, yet, in this specific instance that doesn't work. You can latch onto it, but tug all you want: it won't budge.
Given how long this thing has remained a mystery, fans have collectively decided it's almost definitely a bug. Thus if the chest can't play by the rules of Breath of the Wild, neither will its most dedicated players.
As such, YouTuber Leonardo Ramallo used an emulator with a modded save file to clip through the water so they're standing on the seafloor. Even doing this the game still usually won't let Link open it, but if you get him perfectly positioned he'll clip through the ground just enough to allow the open prompt to work.
And what do you get for this fourth wall-breaking feat?
An opal. You get an opal.
That's it! Just a common shiny ore that can be found in countless deposits across the map.
So there you have it. Clearly it's an error in the game's programming and not a complex puzzle or a secret saved for future DLC. Just a run-of-the-mill mineraloid buried at sea.