I've been fortunate to see many sharks during dives on the South Coast of KwaZulu-Natal, South Africa. During the past 5 years I did 26 "shark dives" on the Protea Banks... 2 were baited dives and 24 were non-baited dives. During these dives we've seen Zambezis (Bulls), Raggies (Sand-Tigers), Tigers, Black-Tips, Scalloped and Giant Hammerheads.
All of these dives were drift dives and during baited dives one tends to be in a vertical position. From experience I've learned that there is no difference in a shark's behavior towards a diver if he/she is in a horizontal or vertical position.
Shark diving and encountering a shark underwater is all about common sense. Prior to these shark dives, the DM
WILL gives a full brief on what to do and what not to do when encountering sharks. The dive operator has been operating on the Protea Banks, KwaZulu-Natal for the past approximately 14 years, doing hundreds of shark dives, without any negative incident.
I think that in countries like South Africa, with many potential shark sightings, it's important to have a shark awareness lecture as part of the OW course. In South Africa divers can enroll for advance shark awareness courses that entail theoretical lectures and practical shark dives as well. I did such a course 2 years ago with the Natal Sharks Board and it was an eye opener. The more knowledge you have about shark behavior the more relax you will be while encountering a shark... but
NOTHING beats experience!!
Have a look at my Dive Report, which I've posted after my previous shark dives earlier this year:
http://www.scubaboard.com/forums/africa/279848-trip-report-protea-banks-south-africa.html