According to Greek mythology, which sea monster created whirlpools in Sicily's narrow Strait of Messina?

Charybdis (Ancient Greek: pronounced Kharubdis) is a sea monster in Greek mythology. Subsequent scholarship has suggested that it was based on a whirlpool in the Strait of Messina.

The sea monster Charybdis was believed to live under a small rock on one side of a narrow channel. Opposite her was Scylla, another sea monster, that lived inside a much larger rock. The sides of the strait were within an arrow-shot of each other, and sailors attempting to avoid one of them would come in reach of the other. To be "between Scylla and Charybdis" therefore means to be presented with two opposite dangers, the task being to find a route that avoids both. Three times a day, Charybdis swallowed a huge amount of water, before belching it out again, creating whirlpools capable of dragging a ship underwater. In some variations of the story, Charybdis was simply a large whirlpool instead of a sea monster.

Through the descriptions of Greek mythical chroniclers and historians such as Thucydides, modern scholars generally agree that Charybdis was said to have been located in the Strait of Messina, off the coast of Sicily and opposite a rock on the mainland identified with Scylla. A whirlpool does exist there, caused by currents meeting, but it is dangerous only to small craft in extreme conditions.