Hello, I would recommend you get your rental car through Go-Hawaii, which will link you up with a major car rental company with a good discount. They linked us up to budget which allows you to have 2 drivers for no extra charge. Since you are coming in on a cruise, your time will be limited. I would suggest several things that you can fit into 1 day. Wings over Kauai offers an aerial view of the island and takes about 2 hours from arrival, check-in. This flight cost us about 125 per person a couple of years ago. It is less than a helicopter tour and is just incredible. It quickly gives you an overview of the whole island and is truly spectacular! As driving from the car rental is not far (~20 min at most with traffic I think), you want to go to Wailua Falls. It only takes a few min to see the falls but is just beautiful. These are the falls in Fantasy Island. Waimea Canyon is toward the south will take about 3-4 hours round trip with time to take pictures. The vistas at 2 look out points are not to be missed. If you go to the North Shore, it will take quite a long drive, and the part that you need to know is that after 11 am, you can be stuck in traffic and it could take 1-2 hours just to get back to the airport. For some reason the traffic jams daily and so don't go by mileage or you could have trouble getting back on time. If you only have 1 day and decide to go to the North shore, you could rent bikes and ride the coastal trail which is just breathtaking and a lovely bike ride! We rode bikes from the Hilton Garden Inn but there are many other bike rental places nearby. If you do go to the end of the road on the North shore, you should try to see the Limahuli gardens (about 1 hr) with spectacular views and lush scenery. If I only had 1 day and I wanted to pack it in and were on a budget, I would do the Wailua Falls, followed by bike ride, and then go to the Canyon. Whatever you do, do NOT go to the Fern Grotto. There aren't many ferns to see and it is the biggest rip off on the island. If you have time, stop to taste the rum at Kilohana plantation (near the airport and not far from cruise terminal). Ask to try the coffee rum. If you just want to have a beach day, go to Shipwreck beach (near the Hyatt). Lovely hiking trail there if you are up for it that goes past a cave and down to the beach. Good Luck!

We used Na Pali Catamaran in October (2016) and took the 7:00AM tour. We highly recommend it. Depending on the time of year you go makes a difference too. If October-April, I read that it is only recommended to take a tour from the north end and not every place will go out. We did and it made great use of our time --4-5 hours included tour and a snorkel stop including pre-ordered sack lunches. I also highly recommend the earliest tour. (We were staying on the south tip of the island and it did take an hour to get up there-but we also were ok due to trying to do as much early in the day as possible as home was on EST). The water gets rougher as the day goes on (anywhere on the island we found) and motionsickness will be tougher to fight. One benefit of Na Pali Catamaran is that the cat is bigger than the rubber boats, so you can stand or sit at any point. It also had a covered area for shade. And the cat was small enough to be able to duck in and out of several caves along the way. Lastly the company was professional yet quite fun and instilled confidence in us as customers. We saw two different pods of dolphin the morning we were out and it was fun to see the crew taking pictures and to be as excited as were to see them! Lastly- they will not go out if weather is bad or too rough. Our original scheduled date was cancelled 2days in advance because of high surf. They offered to reschedule or completely refund. I respect their judgement. With that said, if this is a priority for your trip like for us, schedule early in your stay in case of needing to reschedule. I hope that helps! Since we just got back, the opportunity to answer your question was great!! We miss it already! Feel free to ask more questions to me if you have any. We are a family of 4 including twin 14 yr olds if that helps.