Most of them were submerged due to flood, others were the result of waterways and reservious constructions.
Port Royal, JamaicaA massive earthquake, followed by a tsunami submerged the city of Port Royal and killed 2000 people.
Dwarka, IndiaAlso known as the Gateway to Heaven, the city of Dwarka was, reportedly, discovered in 1988, submerged around 100 ft below the Gulf of Cambay.
Baia, ItalyThis submerged underwater city is believed to be the city where not pirates, but hedonistic Romans used to flock to Baia.
Pavlopetri, GreeceBelieved to be the oldest underwater city, Pavopetri was discovered in 1967, which seemed like ancient ruins.
The Lost Villages of Ontario, CanadaThese regions were submerged after the construction of a waterway that was built in the 1950s.
Atlit-Yam, IsraelThe city was discovered in 1984, and that too in 30-ft underwater, where graves, buildings, and odd skeletons were found.