As an amateur free diver, I can tell you from experience that diving along the south side of the island is a hit or miss experience. While you may expect our beaches to have all the fish of Hanauma Bay, it can very often look like an absolute wasteland out there, with currents that can pick up in a flash if you’re not careful.
DO NOT bring your spear out unless you’ve read up on the fishing laws- as killing an undersized fish is a huge taboo both in the eyes of the law and the locals. A good general rule of thumb is to learn about which areas are safe to go to- stay away from Waikiki and Diamond head beaches during odd numbered years (2015, 2017..), as well as certain conservation areas in Waimanalo, and that’s not all of them. Here’s a link to the Division of Aquatic Resources map of conservation areas: http://dlnr.hawaii.gov/dar/fishing/fishing-regulations/regulated-areas/regulated-fishing-areas-on-oahu/
However, when you happen upon an area fraught with fish there is nothing like diving on Oahu. Just be sure to watch out for the boats as well- who frequently are unable to see the flag of a diver, and as such should be given an extremely wide berth.
Snorkeling through Waikiki can be an amazing experience when the waves are extremely flat- 0-1 feet ideally. You can find some basic information by searching for various surf and tide reports on the island of Oahu, usually by googling something like “surf report Oahu Waikiki”. Even though the report may say one thing, and the camera on the beach may make the ocean seem placid, always be very aware of the currents, your relation to to shore, and your partner- going alone is very risky.
In the next decade or so, the government in Hawaii will completely ban sunscreens that kill the reef- which will most likely include many of our favorite products. If you happen to get the opportunity to dive in Oahu though, you may come to the realization that some changes definitely need to be made, as our reefs are struggling to survive the surge of destructive chemicals and over fishing. Lets all do our part to malama ‘aina, care for our land.
Also- don’t touch the turtles. Big fine.