There are organized excursions in which you will not only get to know the Gulf of Kvarner, but also the broader region, or you may simply drive your own car to Rijeka, Istria, Plitvica Lakes, Krk, Cres, Pula, Trieste, Lipica.
Organized trips around Istria:
http://www.istriawinetour.com/
Boat trips:
https://www.paragvaj-tours.hr/
https://www.contessa-tours.hr/
https://www.magic-fly-tours.hr/izleti-brodom
Taxi boat:
Travel agency: