I had the pleasure of ending my time in Tanzania with a trip to Chumbe Island, just off the coast of Zanzibar. This tower, called the Lighthouse, is the biggest structure. But there are several wonderful open-air bungalows that you can book for a relaxing stay. The snorkeling is amazing among the island's pristine reefs.
OK so I'm a nerd! I thought the design of the dwellings on Chumbe Island were so creative - oriented to catch the breezes, completely open but secure, stairs to keep out the numerous (and curious) coconut crabs, and completely eco-friendly!
Chumbe Island has amazingly pristine coral reefs. While out snorkeling, it's wise to remember not to touch the reefs or the creatures that live there (like this big bivalve - especially since if it clamped down on your hand or foot you might be stuck there beyond your lungs' capacity!)