The route and duration would depend of weather conditions and the group fitness level - but we normally do a loop to different beach for swimming/snorkeling/ and than we return to the starting point. Boat back to Hvar.
Total about 4h. Boat transfer is about 15min each way.
On the starting beach there are also few small restaurants/bars (cash only) if you would like to have a drink or stay for lunch after kayaking..