The bay is the reason Pemba exists. A great horseshoe of water about ten kilometres across, sheltered by the headland to the south and a long arm of land to the north, it is one of the largest and deepest natural harbours in the world. Cargo ships, dhows and small fishing boats share the same protected anchorage.
For travellers the bay means flat, glass-clear water — almost always swimmable, often spectacular for snorkelling. A morning dhow trip out to a sandbar in the middle of the bay is one of the easiest and best things to do in Pemba.