prokayak,
I fished in Nungwe in the North, on the east side and down by Kizimkazi in the South. The west coast is a little barren and i did not catch much there.
At low tide you can wade to the edge of the reefs and fish the pushing tides; not too many fish, but there are quite a lot of 2-4kg kingfish which will clap drop shots.
Make sure you take some good wading shoes.