Hi, Nordic Friend!! so..Erba is near Switzerland border (almost 10 KM).Therefore you are at the top of Northern Italy. If you wish have a nice swimming in Ligury , it takes form Erba at least 350 KM for reaching west Ligury via Milan (The famous and pretty CinqueTerre....very amazing...very). So, if your preference is for the Adriatic Sea instead, less amazing than Ligury but full of entertainment and good for kids , it takes more than 450 KM for reaching Rimini and so on.
I suggest you to visit Ligury 5Terre....is more near, a bit more expensive than Adriatic Sea but unforgetable....you will fall in love !!!!