There is extensive ferry service among the islands. We took a 1.5 hr ferry between Papeete and Moorea (then flew to Bora Bora). Ferries are cheaper than flying and more picturesque in some ways as passengers get to see several islands along the way for the longer journeys. I recall there was a relatively convenient way to get from Papeete to Bora Bora in one full day and then to return in one full day. Possibly even an overnight ferry! However, scheduled ferry service did vary by day of week.