Thucydides, History of the Peloponnesian War
Benjamin Jowett, Ed.

24. Meanwhile in Sicily the Syracusans and the allies brought up the fleet which they had¹ been equipping² to Messenè, and joining the other fleet which was keeping guard there, carried on the war from thence. [2] They were instigated chiefly by the Locrians, who hated the Rhegians, and had already invaded their territory with their whole force. [3] They were eager to try their fortune in a naval engagement, for they saw that the Athenians had only a few ships actually on the spot, the larger portion of the fleet which had been despatched to Sicily being, as they heard, engaged in the siege of Sphacteria. [4] If they conquered at sea they hoped to blockade Rhegium both by sea and land; they would easily master the place, and their affairs would then be really gaining strength. Rhegium, the extreme point of Italy, and Messenè, of Sicily, are close to one another; and if Rhegium were taken the Athenians would not be able to lie there and command the strait. [5] Now the strait is that portion of sea between Rhegium and Messenè where Sicily is nearest to the continent; it is the so-called Charybdis by which Odysseus is said to have passed. The channel was naturally considered dangerous; for the strait is narrow, and the sea flowing into it from two great oceans, the Tyrrhenian and Sicilian, is full of currents.