Poipu is a beautiful beach on the south side of Kauai. If you visit the island in the winter, the beach on the north side would be very rough. I would highly recommend visiting Poipu for some wonderful beach time in the middle of December! There are many shops in Poipu where you can rent snorkeling gears for very cheap. Some shops also rent cameras in waterproof cases for underwater photos. I recommend renting or bringing a GoPro, as the quality of those "waterproof cameras" is not great. You can pick up some fish food in those shops as well.