The rock bridge on Oahu is a relatively hot hike since the trail provides practically no shade aside from one tree near the middle of the hike, so be prepared with plenty of water. My friend almost passed out the first time I went because she did not bring water, thankfully some fishermen were kind enough to give us a few bottles. I went with someone who knew where it was so I did not have a problem finding it, however I have heard of people going back time and time again because they were unable to find it. So once again, do your research. My friends roamed around for five hours and did not find it. The hike takes approximately 3 hours depending on your hiking pace. Please be careful as there is a crack going down the entire back side of the rock bridge and the last thing you'd want is to be standing on it when it goes down. The water can get pretty rough so check the tides and wave conditions prior to going unless you plan on looking from afar. 
Splash from the winds created a rainbow in the bottom corner of my picture.
