A whirlpool is a swirling body of water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 usually produced by ocean tides. The vast majority of whirlpools are not very powerful. More powerful ones are more properly termed maelstrom

Maelstrom

A maelstrom is a very powerful whirlpool; a large, swirling body of water. A free vortex, it has considerable downdraft. The power of tidal whirlpools tends to be exaggerated by laymen. There are virtually no stories of large ships ever being sucked into a maelstrom, although smaller craft are in...

s. Vortex

Vortex

A vortex is a spinning, often turbulent,flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex...

is the proper term for any whirlpool that has a downdraft. Very small whirlpools can easily be seen when a bath or a sink is draining, but these are produced in a very different manner from those in nature.