It is a frazione of the comune of Chioggia, which is part of the Metropolitan City of Venice in the Veneto region in north-eastern Italy.

Sottomarina is a peninsula which protrudes into the Lagoon of Venice, forming its southern coastal tract.

The other parts of the coastline of this lagoon are the barrier islands of Pellestrina and Lido, in the middle, and the peninsula of Cavallino in the north.

In the 18th century, the murazzi, the imposing Istrian stone bank was built to protect Sottomarina from storm surges.

The doge Teodato Ipato (742-55) had a fort built at Brondolo to protect the southern end of the Duchy of Venice.

Since then, the southern side of the coast of Sottomarina has been widening at an average rate of three metres a year due to the sediments brought to the shore by the river.

Today Sottomarina is primarily a busy seaside resort, thanks to its proximity to Venice, Padua, Vicenza, Verona and Rovigo.