We get more than 5000 posts a year on trips to Italy, on this forum. Very, very few of them mention swimming in Italy, in the Cinque Terre or swimming elsewhere in Italy, as being something that was a priority, given limited time and all the things Italy offers that aren't easily available in the US (the Canadian experience may be somewhat different because of northern location of Canada's beaches).
Italy offers many, many things the US does not have. But it seems that very few North American travelers use their limited time in Italy for swimming. We have had a few posters here who somehow got an expectation in their brain that Italy has coastline, therefore it must have ocean swimming and I'm going to do it, and a few of these travelers were persistent enough to force ocean swimming into their already crowded itineraries.
It's a matter of personal preference. But it may help to know that, according to the evidence on this forum, very few American travelers to Italy make that choice.
Oregon beaches were mentioned in another post. People who do not know Oregon beaches might, erroneously, reason: Oregon has beaches, therefore it would be reasonable to expect to swim, and enjoy it, while at Oregon beaches. Flat out wrong.
Water temp is influenced by water currents and not just by miles of latitude south. For example, going from northern to southern Oregon, several hundred miles, does not get you to comfortably swimmable water. That's probably also the case in that part of Italy: if a person thinks the CT water is not comfortable, then moving south from the CT probably does not get you to water you'll like.