Hey mate I went there in December, stayed in Waikiki for a bit but for the most part on the North Shore.

Just north(10 min walk) of the main Waikiki beach is the marina and all along it there are heaps of charters running these little booth things that you go up and book with. It is quite exxie though as you book the whole boat, it's not like here where you and 20 others jump on a cray boat. I didn't go on one though but wish I had, so i cant recommend any in particular. They also run some charters out of Haleiwa on the North Shore, that might be worth a look as that time of year it's nice and flat up there.

North Shore for sure. Don't bother with the Waikiki charters. If your really keen. Book a flight to the big island (Hawaii) and charter fish from the north shore of it. One of, if not the most, consistent catch rate areas for billfish in the world. I wanted to do it last year but pulled out because it wasn't billfish season. In May you should be right.

Try Maggie Joe, http://maggiejoe.com/   I went out with them 2 years ago & they were pretty good, can hire the whole boat yourself, or go on a shared charter think it was around the $250 pp for shared & only 6 on the boat. Is mainly game fishing not bottom bouncing over there.

There are several charters.  Last one I went to many years ago was infront of Ward Warehouse, by the Boston Whaler Dealer.  239lb Yellow Fin Tuna that took forever to boat.  Oh BTW the skipper keeps the fish, not you.

Thanks guys for the info, I might try and jump on one of those share boats as I think the mrs would rather stay on land and I don't wanna pay for a whole boat.
Sounds like the fishing is pretty decent there

Unfortunately it was on film as that was 28 years ago.  Will scan it if I dig up the photo album.