The Kornati archipelago is a beautiful Croatian national park with 140 largely deserted islands to explore. Populated by only two people in the year, it's a paradise for yachtsmen. I was also lucky as I was able to visit some of these completely deserted islands by boat and enjoy private beaches in an exceptional environment.
It's also one of Croatia's most fabulous spots for underwater diving. Because of the lack of civilisation, the seabed is very rich and I've had no problems swimming from one island to another with the only background noise being the lapping waves.
It's a real paradise on the Croatian coast which, due to the lack of connections to the mainland, is unfortunately not accessible without a boat. But if possible, you really must go and discover it during your stay, especially as some travel agencies offer trips to the archipelago when you holiday in Zadar.