Hey Nori..I just spent 3 weeks diving Tofo/Barra/Zavora in Moz in April/May and loved it! Some of the best diving I've done outside of SE Asia/Australia...not just for the big stuff its famous for, but also for great and rare macro (rhinopias, harlequin shrimp, etc.). That was my first and only visit to the area, so I can't speak for conditions August-December, but it was my understanding that's generally considered prime whale shark season (we didn't see any, although saw lots of mantas), with water temps in the upper 20s. I think that's out of typhoon season as well. Due to the plankton in the water that attracts the whale sharks/mantas, you're never going to have crystal clear visibility there, but I don't think one time of year is necessarily better than other. Dove with, and highly recommend, Peri Peri Divers www. peri-peridivers.com. If you email them I'm sure they'll be happy to answer any other specific questions you might have. If you want any other info, or if you're planning on going into South Africa to dive on your trip, feel free to pm me. Have fun!