I did not hit this site, which was directly off Haliewa Beach Park, very often. Usually if I made the trek all the way to the north shore, I'd go to Pupukea. But the Trench was an interesting spot. After entering the water from the beach, a short swim over the shallow reef would lead you to a sharp drop into the Trench, an elongate cut in the reef that bottomed out close to 30m or so. The walls had ledges and small caves the the bottom some sand and coral. You could also cross the channel to its outer edge, but as I remember, it was mostly live coral out there. I crossed it a couple of times, but that was usually on snorkel enroute to dive sites much farther offshore.
While I found a few nudibranchs here, at night this site was the only place I dove on Oahu where you could regularly see the Hawaiian version of one of the chick pea cowries, now known as Pustularia cicercula takahashii.
It is also possible to see some of the shallower water opisthobranch species under rocks on the shallow reef between shore and the Trench. Specimens of Actinocyclus verrucosus and Thuridilla neona were found here.
Close tab when finished.