Catching a ferry from Venice, Italy to Porec, Croatia

WE'RE TWO COUPLES PLANNING A TRIP TO CROATIA IN MAY 2018, CONSIDERING FLYING INTO VENICE AND A NIGHT OR TWO THERE BEFORE CATCHING A FERRY TO POREC. ARE THE FERRIES RELIABLE? CAN YOU RECOMMEND SOME THINGS TO DO IN VENICE? N. DOMBKINS, SALAMANDER BAY, NSW

According to direct ferries (directferries.com.au) there are two ferry lines operating between Venice and Porec offering a daily service. The crossing takes around two hours. Ferries are reliable and you might want to book your ticket now to avoid the possibility of a price rise.
Two nights in Venice gives you only one day and that's not enough. I suggest four nights minimum. Venice is a knockout. A city tour is essential and the local tourist office has several walking tours led by expert guides. You can find a tourist office in St Mark's Square and there are others. There are several possible themes, most of which include the distinctive food of Venice. Other "musts" would be the Penny Guggenheim Collection, Musica a Palazzo (palazzovitturi.com), a trip across the lagoon to Burano and go early in the morning, the Rialto Market and plenty of time taking ferries, hanging around in cafes and wandering around in a state of amazement – it's that kind of a place.
Accommodation in Venice is fantastically expensive but you can get far better value if you stay in Mestre, preferably somewhere close to the station, and take the train into Venice.