Freek is alluding to this thread http://spearfishing.world/showthread.php?t=57 :DWere you using a depth finder? If not I'm sure there's lots to be found still.
I scanned the thread above, thought I'd write here, just so people aren't like, "who the hell is this guy?".
The problem is: there is no right or wrong. This kinda falls under "etiquette". In my book, whoever spears the fish has "rights" to it. With that said, if I was Diver A - I'd offer the fish for sure.
I'll put it this way: Boat owner maintains the boat, provides labor, invites you on a trip. Boat owner drops you on his "secret" spot, while he takes the first turn driving the boat for drift diving. You shoot a nice Mutton and some Mangroves. Time for the next spot, but the boat has engine trouble, so you head in. Boat owner has to make repairs on his boat, etc...
My point is, even though someone else did most of the work for the shooter to get a fish; he or she is not "entitled" to the fish. Now, etiquette/being a good friend says give the boat owner a fish or two, gas money, beer, etc, but that's at the discretion of the shooter.
I was just making an analogy and trying to give my opinion clearly. As always there are lots of subtleties that make it complicated. My $0.02.