Mozambique is rich in terms of diving options. The best sites for snorkling and spearfishing near Maputo are: Inhaca, Banco do China, Wreck and Santa Maria. My divers are really familiar with them.
There are also lots of good diving spots outside Maputo, being the most famous: Inhambane, Baía dos Cocos (Coconuts Bay), Santa Carolina, Inhassoro, Ponta da Barra and Tofo.
One of the most exotic places to dive is Bahassas da Índia, a very small French athol in Channel of Mozambique. It has the curious feature of disappearing when the tide rises. During old times the place was a trap for navigation, that’s why it is so easy to find artifacts from sunken ships still there, such as nails and anchors.