The high-water mark hit 74in late on Tuesday, meaning more than 85% of the city was flooded. The highest level recorded was 78in during infamous flooding in 1966.
The governor of the Veneto region, Luca Zaia, said one person died, although the cause was not immediately clear.
Photos on social media showed a city ferry and taxi boats grounded on walkways flanking canals. Already on Tuesday, much of the city was under water, inundating the famed St Mark’s Basilica and raising new concerns over damage to mosaics and other artworks.
Officials projected a second wave as high as 63in at mid-morning Wednesday.
Venice mayor Luigi Brugnaro blamed climate change for the “dramatic situation” and called for a speedy completion of a long-delayed project to construct offshore barriers.
Called Moses, the moveable under-sea barriers are meant to limit flooding of the city, caused by southerly winds that push the tide into Venice, but the controversial project is opposed by environmentalists concerned about damaging the delicate lagoon eco-system, and it has been delayed by cost overruns and corruption scandals, with no completion date in sight.
Mr Zaia told SkyTG24 that the barriers were almost complete, but it was not clear if they would work against such flooding.
“Despite 5 billion euros under water, St Mark’s Square certainly wouldn’t be secure,” he said, referring to one of Venice’s lowest points that floods when there is an inundation of 31.5in.
Mr Brugnaro said the flood levels represent “a wound that will leave indelible signs”.