Denarau marina

Denaru is an island accessible via a bridge. A taxi or anybody with a car will bring you there for between 5$ and 15$ depending on your starting point.
This is a large private island owned by the Sheraton Hotel.

From the Marina, there are ferries departing to the Yasawa Islands at 9am only.

If you miss it, you can always go to closer islands such as South Sea Island, Bounty Island or Mana Island in the Mamanuca Islands, you can depart at 9am, 12am or 3pm.