Chioggia is very old. According to legend, once Clodio, a companion of the Trojan prince Aeneas, who had fled by 2,000 BC from his destroyed home, settled here. He was followed by Etruscans, Romans and Lombards. Truly sustainable Chioggia was finally captured by the tourists.
While Venice extended its dominion over the Adriatic Sea, Chioggia was destroyed and looted (last by the Genovesi, which you have to keep in spite of all credit, they have invented the good pesto).
So the Chiozzotti decided to leave the district Sottomarina and to withdraw to the surrounding protected through the water island. This led to the further development of the city which was built mainly on fishing (hence the great fish market).
Chioggia has always stood in competition with Venice. There was a time, as they seemed to surpass even Venice.