Kualoa Regional Beach Park is a large, flat, grassy park with a few sandy beaches and the beautiful Chinaman's Hat just off the shore. Tucked up near the Ko'olau Mountains and just across from Kualoa Ranch, the area is relatively remote but still gets a lot of visitors. Located on northeast O'ahu, it's about halfway between Kaneohe and the Polynesian Cultural Center in Laie. The multi-section park is a 150 acres total, so it can handle a lot of people and has a ton of parking. There are picnic tables, a bathroom, and showers. There is a lot of great seabird watching, especially at the nearby Moli'i Fish Pond.
The water over here is usually pretty calm, but it is rocky just off the sandy beach. During low tide you can actually reef walk (wade in shallow water) out to Chinaman's Hat (Mokoli'i Island), but the tide comes in quickly. There is no surfing here but plenty of opportunity to paddleboard and kayak. The area has historic significance and was a training ground for certain ali'i (chief) in the past. Check out this website to book Kualoa Beach Park A campsites, which is a lesser known tucked away section.