On TA we all spend a lot of time doing the merits of Plitcie vs. Krka NPs. If you want a completely different experience then Paklenica NP is found between the two, not far from Zadar. Described as 'Where the mountains meet the sea' all I can say is that this is a completely true description. Lots of excellent walking trails, rock climbing which is great to watch and opportunities to mountain walk high up and see the stunning Velebit mountains. You can stay out in mountain huts too. There is a also a great cave to see - Manita pec - with stalactities over a million years old.
Stay locally in Starigrad Paklenica or Selene and swim in the sea after an energetic day. Lots of accommodation available. There are also low level walking trails along the edges of the national park which go via small partly deserted villages.
If you want a NP that isn't all about visiting water - choose Paklenica.