Hi Steve,
hammerheads in the Red Sea are quite unpredictable and rare compared to the Cocos Islands.
The scalloped hammerhead (Sphyrna lewini) seems to prefer cooler water and is usualy encountered at depth, below the thermocline in summer months. Schooling hammerheads are usually seen in the early morning and tend to be out in the current off a promontory on the reef. About hammerheads habits is little known, but there is some ways how to come closer. After few attempts, we found their way around, the appropriate season are end of June or July, the initial observation depth is 30 meters.
We had a lucky that we can observe in a row of three mornings at the same location, once also over 17 hammerheads lewini together. They are very frightened and complete divers standstill is a must. Apparently they do not interfere with divers bubbles, because they come very close to us. On the video clip there is a large group of divers in the water which reduces the possibility of meetings.
The biggest problem there was very strong current, who can easily move divers from the reef, which is in open sea extremely dangerous. Rescuing lost divers in rough open sea is mission impossible.
/peter