If your travel agent reffers to any of the Egyptian Red Sea as "deep south Red Sea", beware! It clearly reveals that this person doesn't know a lot about Red Sea diving. Anything in Egypt, Jordan and northern Saudi is northern Red Sea. Sudan, Eritrea and parts of Saudi is central Red Sea and Yemen+Djibouti is southern Red Sea. Diving is possible in all countries, however many of them are a bit more complicated to arrange trips to. The easiest choice is Egypt (I'm not taking Israel into the picture since the diving there is inferior compared to the other countries) which has a lot of good diving. Sharm or Hurghada are in the northern part of Egypt, not very cosy places, but good if you want to be able to visit a pub at night.
However, for any seriuos diver a liveaboard is the best way. If you suffer from seasickness, try the camps in the southern part of Egypt, near Marsa Alam. Most diving is done from shore, but the african trench makes waters close to land very deep, so big fish is a possibility (like Ras Mohamed in Sharm El Sheikh).
For liveaboard diving, I would reccomend the MY Royal Emperor. It has nothing to do with Emperor Divers as indicated in an earlier posting, but is a very well run ship with AC, E6-processing, NITROX and even an rebreather for hire! The crew is flexible and the food good.
www.royalemperor.com It is owned by a very nice egyptian gentleman who's name is Yasser El Moaffer, an enthusiastic diver who understands what a seriuos diver wants from a trip. My favourite dive area in Egypt is Brother Islands.
For a real adventure in the Red Sea, try the sudanese Red Sea. You can find a posting about this under UW-photography.
good luck
Christian