There are many different boat-lines from Trogir, Okrug Gornji and Split.
From Split you will find regular day trips to some of the bigger and more well-known island such as Brač or Hvar. Hvar is one of the most beautiful islands in Dalmatia, and definately worth a visit. If you like to can also take the boat to Italy - it takes a little more than a day - typically you will sail out from Split in the evening and arrive early the next morning in Pescara. On Jadrolinija you can find more information on routes, timetables and prices, you can also make an online to make sure you will get tickets.
You can sail from Trogir via Slatine on the southern tip
of
Č
You can also to sail to some of the small island around
Trogir and
Č