Rarely in Minecraft Bedrock Edition worlds, massive lakes can generate that go down to bedrock.). In some cases these lakes will have a sinkhole of sorts, big holes at the centre of the lake that do down to lava. In very rare cases they can generate floating aquifers & structures not in their respective biomes (like woodland mansions and villages). If you want to see a sinkhole in game, load up Minecraft version 1.21.51 and enter this seed: 737373737403890284. Fly up at spawn and you will see a big lake with a sinkhole. These sinkholes have a 100% chance of generating a buried treasure somewhere. Sometimes floating in the sinkhole, sometimes at the bottom of the world. In Java Edition these sinkholes do not generate, but the big lakes do.