2324 - Coal torpedos

That's right, you read that right, a coal torpedo. But it's not quite what it sounds like. It accomplishes the same thing just in a different manner. And this isn't new. This is from the civil war.

From the Wikipedia article....

The manufacturing process was similar to that used for artillery shells, except that actual pieces of coal were used as patterns for iron castings. The walls of the coal shell were about 3/8 inch thick, creating a hollow space inside sufficient to hold 3–4 ounces of gunpowder. After filling, the shell was closed with a threaded plug, then dipped in melted beeswax and rolled in coal dust, creating the appearance of a lump of coal.

This was a Confederate invention. The fake coal was placed in the coal piles to be loaded onto the Union steamers. The boilers would then blow up maybe sinking the ship.

They were also used in WWII and Vietnam.