The island was sold by the Arabs especially because slave trade had been abolished. A prison to serve Zanzibar was built on the island and completed in 1894 from where it got its name.
The Island was never used as a prison, instead it became a quarantine station. Zanzibar being the most utilised port town at that time, the authorities were concerned about the threat of epidemics brought by passengers and cargo from across the seas and so the island was designated as a quarantine island.
Today Prison Island is known for its excellent views of Stone Town, there is a beautiful beach, good snorkeling, a ruin and the giant tortoises (= changuu) from which the island gets its Kiswahili name.
Prison Island is a very popular destination, it's a quick 15 minutes boat trip from the old town’s waterfront. Negotiate a ride with any of the waiting boats and take an additional US $5 for the entrance fee on to the island. Ask your boat driver to take you around the back to of the Island for the best snorkelling!
Changuu Island is an ideal half-day excursion out of Stone Town when you have some spare time!