The islands of Tahiti are composed of 118 islands and thanks to the only inter-island carrier @air_tahiti (not to be confused with @airtahitinui) island hopping is more accessible than ever. Air Tahiti is definitely the link between the islands. Are you looking to visit more than one island? Your best value would be to purchase one of the Multi-island passes. Some of the passes available are: Discovery Pass, Bora Bora Pass, Lagoons Pass, and Marquesas Pass.
To get from Tahiti to Moorea these ferries are great Aremiti or Terevau. You can book tickets online or purchase them right at the dock. If you plan to take your rental car on the boat that will require advance reservations as the car spots are limited.