Fifty of the capital's fountains, including the Barcaccia fountain at the bottom of the Spanish Steps, will be restored between now and the end of September, Marino said on Tuesday.
“Rome has the luck of having dozens of historic fountains and we have decided to restore the top 50," Marino was quoted by Ansa as saying.
"We want to make our city increasingly beautiful and the fountains play a role in decorum and in the welcoming of tourists.”
The mayor also sent out clear message that taking a dip in the fountains is not free, regardless of how hot it is.
Fines are already almost a couple of hundreds euros – the Italian actress Valeria Marini was fined €160 in 2014 for stepping into the Trevi in a bid to mimic the famous Anita Ekberg scene in ‘La Dolce Vita' – and now Marino said he would propose increasing them.
Frustrated Rome residents have also started to take to the internet to shame tourists they spot taking a splash. Alluring though the monuments are, especially in the searing heat, little do they know that it's against the law.
Read more: Tourists in hot water for Rome fountain dips
Those caught throwing rubbish into the monuments will also be fined.
The Barcaccia fountain was trashed earlier this year by drunk fans of the Dutch football team Feyenoord, costing the city thousands of euros in repairs.
Marino has sprung into action following a slew of negative headlines about some of the city's rubbish-strewn streets and chronic transport problems.
The government also said on Tuesday that €18 million would be earmarked to rebuild the Colosseum's arena floor.