The 30-year-old from the Czech Republic stripped off last Friday afternoon, dumping her belongings on the monument -- which pays homage to Italy's war heroes -- as she went for a swim in the freezing lagoon, and then lay beside the statue of a murdered female partisan to pose for photos.
She was banned from Venice for 48 hours and fined $513.
Local Mario Nason was out walking with his son when he saw the woman and her two companions on the monument, which sits on the waterfront.
Dedicated to the women who gave their lives in their fight for freedom under fascism, it consists of a bronze statue of a murdered partisan, half in the water, half on a platform of bronze and concrete. Placed near the gardens of the Biennale, it is one of relatively few statues dedicated to women in Italy.
"It was a beautiful day and we saw two people taking photos. I saw a strange movement and then I saw this woman swimming without a care in the world," Nason told CNN.
"I thought she must be crazy, thinking she could swim on a freezing day.
"But then I saw she was trying to get out of the water by climbing onto the statue, wearing just her bikini bottoms.
"She got up on it, then she got back into the water, totally relaxed.
"Her boyfriend and another woman had jumped over the barrier and were on the monument, to take better photos of her. They were stood there beside her clothes that she'd left [on the monument], just as you do on the beach."
The woman, who has not been named, was apprehended by police. They fined her €350 ($400) and hit her with an antisocial behavior order, including a 48-hour ban from the city, which comes with a separate €100 ($113) fine.