One of the most exciting you can do while in Oahu, is hike the Makapuu Lighthouse Trail. The Makapuu Lighthouse Trail, a part of Kaiwi State Scenic Shoreline, has varying degrees of ease or difficulty, according to where you choose to start and end.
You can drive to different areas to get great views, as well as choose your hikes. There are some paved areas which make it easy to traverse. You'll see miles of coastline to view the vibrant blue Pacific Ocean. If you arrive at the right time, you may even get to see the migrating humpback whales off in the distance.
If you want to do the whole experience and are up to it, the Makapuu Lighthouse Trail will reward you tenfold. If you are really in shape, you can venture the Koko Head Trail which has a crazy stairway leading to the Koko Crater, which is what's left of a volcano from long ago.
Another true adventure is to take, what can be a dangerous trail down to the water. The rocks crumble along the way, so be mindful of your footing along the way. Don't get to close to the waves, as they crash along the rocks. They can cause water to rush up through cracks and crevices from underneath. There are also some spectacular tidal pools to take a dip in. However, if it is a particularly rough wave day, you may want to see these areas from afar, as it can be dangerous.