The only practical way onto Moorea is from Tahiti.
By ferry — The Aremiti and Terevau companies run a high-speed catamaran service between Pape'ete and the Vaiare terminal on the east coast of Moorea. The crossing takes 35–45 minutes, with around five to eight departures a day; one-way fares are around 1,500 CFP. This is what almost everyone does. Vehicles can be brought on board for an extra fee — useful if you are bringing a hire car from Tahiti.
By air — Air Tahiti operates short hops from Pape'ete to Temae airport on the northeast tip of Moorea — about ten minutes of flight time, mostly used by connecting passengers from other Polynesian islands. The fare is several times the ferry price and the time saving over the catamaran is negligible once airport procedures are factored in. Worth it only for onward connections, particularly through to Bora Bora or the Marquesas.