We've only taken one diving vacation in Mozambique—specifically, in Tofo on the southern part of the country—so our experiences are limited. What can we say with just this experience?
We dove with Diversity SCUBA. We don't have anything particularly negative to say about Diversity. As for the positive, the equipment was functional (though we brought mostly our own) and the ratio of guides to divers was a good one: usually one guide per two or three divers. All of our dives were with nitrox, and they provided choices in 12 or 15 litre tanks, steel or aluminium. They even had hot showers, which travelling divers know is a real treat after diving in non-tropical temperatures regardless the exposure suit. No twinset or side-mount diving, however; no passing NDL; no dry suits. Simple recreational dives.
What should you expect in diving on Tofo? First, limited visibility. Second, current. Third, swell. Don't misunderstand: there's marine life in abundance! It's just that often the conditions are not optimal for really… seeing it. Though they're certainly good enough. On the topic of the current and swell, we don't recommend Tofo for anybody uncomfortable (or unfamiliar) with strong currents and surge, both at the surface and at depth. We watched as a lot of fellow divers (with only a handful of prior dives!) were bashed along the bottom. And side of the boat. And other divers. And marine life.
And do bring a cold-water wetsuit: the temperatures, at least during our stay, dropped to 21 or 22 degrees. Warm to some; but to us, quite cold.
On the topic of marine life and megafauna in particular, we saw plenty of whale shark (Rhincodon typus). We'd gladly spend (and did spend!) hours on the surface just swimming nearby these beautiful sharks! Be warned, however: they make look sedate, but they're moving quite fast. We saw momentary glimpses of manta rays, devil rays, a guitar shark, some grey reef sharks, and so on.
Should you go diving in Tofo? Taking into account our limited experience, yes—if for nothing else, to spend time with the whale shark (Rhincodon typus). We probably wouldn't go twice, however. All of this aside, Tofo was great to visit as a destination in and of itself. We wish we'd been able to go surfing!