I had a horrible experience trying to use Nui Tours. We were approached by an employee at about 10:00 AM telling us that even though we missed the 8:00 AM full island tour, we could go on a shorter but "private tour" at a discounted rate (Which was only $30 cheaper than the full day tour). The said employee offered us the opportunity to select multiple places to visit from the full-tour agenda within a 4.5-hour window. We agreed and started the tour.
Upon meeting the combative and rude "tour guide" we could sense that something was off, and we learned that he was not a professional guide and he was a taxi driver that was contacted by the Nui Tour employee. The taxi driver refused to take us to places we wanted to go. We asked the taxi driver to return us to where we had paid for the tour and asked for the money back. The employee was rude and pretended that the "miscommunication" problem was on us, but it was clear that he was doing this for personal gain and not for an approved service by this tour company.
Later, we approached another Nui Tour employee and notified him about this situation. The new employee reiterated that the company only offers the full-day island tour and that the said employee was acting for personal gain. The company should look into this.