My son and I saw hammerheads when we dove in the Red Sea summer of 2016. We were on the Agressor (2 successive weeks). There were songles on each trip and they all had a good time. We were new divers then (just started the October prior... 40 dives or so) and the diving was just fine for newer divers, but they do want to see an AOW cert (maybe just Deep might do) for the deeper dives... and Nitrox may make sense as the dives add up fast. . Some negative entries and some good current in some drift dives, but no anchoring yourself to a ledge in ripping current and if you miss it you're blown out to outer space or such a thing...
So we saw hammerheads several times, but never really up close. One caveat seems to be that as soon as one dover swims after them it is assured they won't come closer... or so at least the DM said.
Overall, we saw a lot. Good trip. Many more boats in the Red Sea, not just Agressor. Reading and shopping a bit more may be worth you while.