Yes, that can happen on the Adriatic, too. But fortunately bad weather conditions don't last long in this area (unless you live in Udine). When it rains, we can recommend the following activities:
You will be amazed how much in particular children and young people are unbored by some laps of indoor go-karting.
Who knows what this city has that it develops its own special charme at any weather condition. Even floods become an exciting event here. Nowhere else but in Venice, you can experience that rubber boots are sold in kiosks as commonly as chewing gum.
The stiff upper lip would probably call it "making the best of it". The front desk of your hotel you will be happy to assist you finding a local diving school.