I read this in another forum:
"For the freshest local hawaiian fish contact Michael Kealoha, owner of North Shore Fish Express in Haleiwa. He runs a fresh fish market and delivery service on the North Shore of Oahu which serves fresh ahi, ono, mahi mahi and more to haleiwa and the surrounding towns. His number is (808) 673-3391."
If you are closer to town, there are other markets that sell fresh fish - like Tamashiro or Chinatown
Make it a fun day at the beach - buy your own fish and a disposable hibatchi grill, bust out the libations, watch the sunset and enjoy