Daily sea level data of the Venice Lagoon observed in the 18th century allow us to obtain a composite the time series of sea level anomalies relative to the mean sea level, spanning 1751--1769 and 1872--2004. From these data the frequency of remarkable storm surges is estimated. They appear to be more frequent in the second half of the 18th century than in the late 19th and 20th centuries. The historical flood on 4 November 1966 turns out to be the most severe during the entire period.