World-famous St Mark’s Square, a magnet for tourists, has been closed, and schools are shut for a third day.
The 187cm peak on Tuesday was the highest level for more than 50 years, damaging cultural monuments, businesses and homes. More than 80% of the canal city was flooded.
The government declared a state of emergency in the Unesco world heritage site.
Residents with flood-damaged homes will get up to €5,000 (£4,300; $5,500), and businesses up to €20,000 in compensation.
Desperate measures as water seeps everywhere
Within a couple of hours, the murky green water of the Grand Canal had risen level with its bank, slapping over the paving stones as boats went past.
Nearby streets quickly flooded. Tourists, shoes covered in plastic bags, carried their luggage along raised narrow trestle walkways, which the authorities have put up to keep the pedestrian traffic moving.
On either side, dirty water continued to rise. At ground level, in their rubber wellies, business owners were already starting to operate small pumps. Many had raised the flood barriers across their doorways – apparently to little effect. Water was already seeping up to ankle height in the souvenir shops and cafes.
“It hurts to see the city so damaged, its artistic heritage compromised, its commercial activities on its knees,” Prime Minister Giuseppe Conte, who visited Venice on Wednesday, wrote in a Facebook post (in Italian).
Fondamenta Zattere – a long, much-loved waterfront area where tourists enjoy strolling – is also under water.
The government has pledged to release €20m in aid for Venice.
Only once since official records began in 1923 has the tide been higher than it reached this week – hitting 194cm in 1966.
The mayor of Venice, Luigi Brugnaro, blamed climate change for the flood, saying the impact was “huge” and would leave “a permanent mark”. Strong winds lashing the area are contributing to the crisis.
Mr Conte said the government would accelerate the building of structural defences for the city, referring specifically to the so-called Mose project – a hydraulic barrier system to shut off the lagoon in the event of rising sea levels and winter storms.