Because Croatia makes up the vast majority of the Istrian Peninsula, it goes without saying that most of the dive sites you can enjoy in Istria can be found there.
Wreck divers will rejoice in the surplus of vessels that are available for exploration. Several ships date back to the early 1900’s, like the Baron Gautsch and the Flamingo. The Coriolanus sank in 1945, and was believed to be a British spy ship.
Check out the caves at Fraskeric, where you can make your way through rocky tunnels. There are also caves to see in Reff Stoja and Valovine, the home of serene grottoes and underwater canyons.
Once in the country, get around via bus, which are efficient and economical in Croatia. Along the coast and between the islands, ferries are the way to go.