Tutorial:Igniting TNT underwater

Making TNT explode underwater seems impossible, especially if you're not using the Minecraft Education. However, with this special technique, you can create explosions even though you're in water!

Materials needed

• 1 sand, gravel or any color of concrete powder
• TNT
• a flint and steel or fire charge

Steps

1. Find any body of water. It could be a lake, river, or in the middle of an ocean.
2. Place the TNT block, with a block of sand or gravel on top.
3. Ignite the TNT with your flint and steel then step back and watch the magic happen.

Gallery

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  Materials needed to make TNT explode underwater.

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  The first design, using sand.

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  The second similar design, using gravel instead.

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  Another similar design, but using concrete powder.

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  Activating the TNT in the third design.

Explanation

The reason that this works is that the TNT does not actually explode inside water, but inside the sand/gravel block. When the TNT is ignited, it becomes an entity, meaning another block such as sand or gravel can fall in and occupy its space. Normally when a TNT explodes underwater, the high blast resistance of water shields adjacent blocks from explosion, But when it explodes inside sand or gravel which has a low blast resistance, the explosion is no longer shielded and can destroy adjacent blocks. This phenomenon was reported as a bug to the official Mojang bug tracker, but was resolved as "Works As Intended", meaning it is an intended game mechanic that doesn't exploit any glitches.

This bug previously would require blocks around the TNT to prevent it from straying too far from the block that fell on it, but it doesn't anymore as the TNT barely moves two pixels. On Bedrock Edition, though, the TNT moves further from the block. Though it may not be necessary, it would be good practice to place a block or two to align the TNT correctly.

Video tutorials

OMGCraft's design:

A more expensive, but simpler, method

Sideways view

Surround the TNT by blocks with low blast resistance, or dig a one-block hole in the ground and place the TNT inside, so that no sides of the block, except the top side, touch water. Then cover the top of the TNT with a redstone block to activate it. Redstone block was chosen because it is the only source of redstone signal to function underwater, not counting the USB Charger Block.