Almost the whole shore zone of the Lake Victoria is prohibited for swimming because of bilharzia. The bilharzia is caused by small worms, which penetrate the skin. The worms need for their development some pond snails living on the plants in shallow water. That's the reason, that only few meters on the shore have a high probability for the infection. The water further away from the shoreline is safe for swimming.
The most islands on the Lake Victoria are bilharzia free too. The resorts on the shore of the lake have swimming pools lying just behind the beach zone.
