In the year 3797 AD, an alien spaceship moved into orbit around Earth and fired a beam of mysterious energy into the center of the Pacific ocean. Over the next several hours, this beam drew all of the water in all of the oceans, seas, lakes, ponds, rivers, and all other bodies of water in the world (including all of the water underground) into one huge column of water that extended up into space.
The beam then shaped the column into a single giant tsunami, forcing it west. It hit the east coast of Asia at a height averaging 200 km. All of Japan was instantly wiped out, then it flowed across Asia, burying everything including the Himalayas and Mount Everest under kilometers of water. It also wiped out Australia and all of Europe and Africa. Then it flowed into the now-empty Atlantic basin and when it hit the East coast of the US and South America it was still 50 km high. It covered all of North, South, and Central America including the highest mountains in Aconcagua and Denali, then flowed back into the pacific.
It kept flowing around the world several times until the water finally settled down (although some of it had been knocked into space and now orbited the Earth). Every living thing on Earth was killed, all of the continents were shattered and reshaped, all of the ice at the poles was melted, and the Earth was now completely underwater except for a few islands.
The aliens thought it was funny.