There are only a few jeeps owned by the resorts or lodge. You can hire a rickety Land Rover with driver near the market in the center of Kilindoni. The street are all still murran, so it could be really fun to wonder about walking and get a bit lost along the main street where you will meet all the locals working, interacting, bicycling, playing, etc. If you are more adventurous you can rent a bike from the place you are staying. The price should be anything from 8 to 15usd/day.
The most fun whatever is to take a typical sailing boatdhow which here do also bus services. They have a wonderful structure all woodmade and usually full of residents with dresses and pots of different bright colors.Almost all diving centers and Lodges will offer you also excursions around the Island.