Things are pretty mellow at Kalae'o'io Beach Park. On the often busy island of O'ahu, it doesn't get much more laid back than the northeast stretch from Kahaluu to Kahuku. The water is usually very calm and glassy, especially in the morning. The east-facing shore gets beautiful sunrises with the Ko'olau Mountains hugging right up to the beach. Things on this side don't get much attention, and that is what can make it so great. If large white sandy beaches with barely anyone on them sounds good to you, this is your place. There is a grassy park with picnic tables and palm trees overhead, plenty of shade from a bevy of sea-loving tree species, and a curving stretch of beach to take a long walk. Normally there aren't waves in this area and the waterline tends to be rocky beyond the immediate shore, so it would be better for stand-up paddleboarding or kayaking than swimming, though you can probably find sandy pockets for wading. Overall it's just a beach most people pass on their way to the North Shore, but we all know how busy it can get up there. Stop by Kalae'o'io to get away from the crowds.
The beach is on the right side of the road between Kualoa and Ka'a'awa. You can park on neighborhood cross streets.