Minecraft wiki entry for Survival_with_no_enabled_data_packs, associated text: In order to enter the Nether, you must find or create at least ten obsidian blocks, to make the portal. Obsidian blocks are usually found in the Overworld, when water flows above a still block of lava, usually falling from a source block down to either an underground pool of lava or the natural layer of lava on the y-coordinate 11 and below in caves and ravines. If you find none, you may attempt to lead water to the lava by digging a tunnel from a lake, a river, the ocean, or a single water source block to a lava pool or the natural layer of lava, as you have no method of directly transporting source blocks for buckets are unobtainable.