The vortex of water appeared in a harbour off the east coast of Japan after an 8.9 magnitude earthquake struck the country.
Footage taken from a helicopter shows a boat dangerously close to the centre of the pool. It is not known whether there was anyone onboard.
The quake, which hit at 2:46pm local time, triggered a tsunami that devastated all in its path.
Read the rest of the story: Video: Japanese tsunami creates whirlpool.