To explore the small island renting a scooter will do. We had one for 4 hours, which gave us plenty of time to go around the island. We paid 5000 CFP (42 EUR) per scooter which includes unlimited mileage and insurance. Gas is extra.
Wearing a helmet is mandatory, though, and you need to show your driver's license.
Bora Bora has one main road which circles the island. Rent a motorscooter and you can go around the entire island in about 45 minutes. We rented ours at Fare Piti Rent-a -Car next to our hotel. It cost 4350 francs for four hours. It is the best way to see the everyday life on the island, not to mention awesome views of the mountains to one side, and turquoise water on the other. You must see the island this way!