Great thread!
Here in South Africa, or let's restrict it to the east coast, which is where we do most of our diving, you will encounter the following. And this applies to most of Mozambique as well.
1. Surf launches in a
RIB which can be pretty daunting at times. In the hands of a skilled skipper, even the nastiest of breakers can be navigated through but not all skippers are equally skilled. You don't want to be on a RIB operated by a Rambo skipper. For the most part, I actually think the surf launch adds to the experience rather than detract from it.
2. Varying sea conditions (as if that ever needs mentioning). But seriously, at times the sea will look like a mirror, at times it will be a washing machine. You rarely know what you're going to get, especially concerning the underwater conditions. It rarely happens though that the dive is undoable because of the underwater surge.
3. Plenty of coral. You'd want to manage your buoyancy so you don't crash into it. For one, you don't want to damage the coral, but secondly some of it can inflict nasty burns, rashes and the likes.
4. Plenty of critters and creatures, some of which can be pretty dangerous - even the harmless-looking ones.
I have yet to encounter a diver who's befallen serious misfortune as a result of a Scorpionfish sting, Electric Ray zap or Tiger Shark munch, which is probably because none of these creatures are by nature aggressive but also because most divers know to be careful.
5. African sun. Don't underestimate the intensity of the sun here in Africa. I don't know why it should be worse here than anywhere else but the sun here takes steady aim and will nail you wholesale if you don't take precaution.
6. Hawkers. As in most poor countries you should be ready to fend off hawkers everywhere. Some will try to sell you souvenirs, which is fine I guess, but they can be hasslesome. Some will offer to guard your car, which is ridiculous but what can you do? Some will just beg for money. Just know that you cannot escape this fact of life.
7. Guided dives. You will in all likelihood end up on a dive with a designated DM whom you'll have to follow around. This is not always a bad thing and they are often very clued up as to the nice spots on the reef. Sometimes I wish I had more freedom to hang around a spot that I like though.
8. No anchor lines. You'll be following the DM who'll be carrying a buoy line. The boat follows this buoy and consequently, if you can't see the buoy line, you are by definition lost. There have been very few incidents where divers get lost in open seas but the thought of it is sufficiently frightening that I do my level best to remain within sight of the buoy line and also carry my own SMB with me just in case.