A teenage tourist who threw herself into the Grand Canal in Venice from a “vaporetto” waterbus in order to evade a ticket inspector was promptly hit with fines of more than €500 for her illegal dip.

The 18-year-old American woman panicked when inspectors started checking passengers because she had not bought a ticket.

She leapt overboard but that did not end her troubles – the crew of the vaporetto notified the police, who fished her out of the water and told her that jumping in Venetian canals is prohibited.

The tourist, from Wyoming, was issued with a fine of €450, which she paid straightaway with her credit card.

But there was more to come – she was also stung for €77.50 for not having bought a ticket.

“To ensure the safety of everyone, we have a constant police presence around the embarkation points on the Grand Canal and on the other main canals,” said Luigi Brugnaro, Venice’s mayor. “Venice must be respected by its visitors”.

The lagoon city faces a constant challenge in reining in some of the more unacceptable behaviour of tourists, from swimming in canals to jumping off the Rialto Bridge and snacking in St Mark’s Square.

Florence, also inundated by visitors, faces similar problems, and announced this week a ban on tourists sitting on the pavement and in shop doorways to eat pizza, panini and other snacks.