Tour Guide
Aldabra giant tortoise on Changuu Island near Zanzibar, Tanzania

Historic Building

🏛️ Changuu Prison Island

A colonial prison that never imprisoned anyone, now home to giant tortoises that were alive before the First World War

Photo: Bjorn Christian Torrissen · Wikimedia Commons · CC BY-SA 3.0

What makes Changuu Prison Island historically important?

Changuu Island — known to most visitors as Prison Island — lies barely five kilometres off the north coast of Zanzibar, a 5-hectare speck of coral sand and acacia woodland with a peculiarly layered history. The island was purchased in 1893 by Lloyd Mathews, First Minister of the Zanzibar Sultanate and former British naval officer, who intended to build a prison for recalcitrant slaves. The building was completed but never used as a jail — some sources suggest it served briefly as a quarantine station for Yellow Fever cases in the early 20th century before being converted to a hotel and beach resort for the British colonial administration.

What Changuu is actually famous for today are its Aldabra giant tortoises (Aldabrachelys gigantea), gifted to Zanzibar by the Governor of the Seychelles in the early 1900s when the Seychelles population was being protected from overhunting. The original four tortoises have grown to a population of approximately 100 individuals, some estimated at over 130 years old. These vast, gentle reptiles — adults weigh up to 250 kg — move across the island's sandy paths in unhurried parades, occasionally pausing to regard visitors with what appears to be profound philosophical indifference. The surrounding reef adds a second dimension: the coral gardens accessible by snorkelling from the island's beach contain healthy hard and soft coral formations sustained by the strong tidal current that sweeps through the channel.

Weather in Changuu Prison Island

Weather data from MET Norway

When to Visit

Boats to Changuu depart from the Stone Town waterfront from approximately 8 AM until early afternoon — the latest practical departure allowing for adequate time on the island before the return crossing. Most visitors spend 2 to 3 hours on the island — enough time for a tortoise encounter, a guided tour of the old prison buildings, and a snorkel. The best snorkelling visibility is at high tide, which varies daily; ask your boatman for the tidal schedule. Avoid the wet season (April–May, November) when the crossing can be rough and snorkel visibility is reduced by rain runoff.

Admission and Costs

Speedboat return from Stone Town: $20–35 per person (negotiate with the boatman or book through your guesthouse). Island entry fee: $3–5 per person (payable at the jetty on arrival). Snorkelling equipment hire: $5–10 if not included in the boat price. A full Changuu trip including boat, entry, and snorkel gear runs $30–50 per person — one of Zanzibar's best-value half-days. The small beachside restaurant on the island serves grilled fish and cold drinks at tourist prices (budget $10–20 for lunch).

The Case for a Guide

  • Tortoise identification and age estimation — guides who work the island regularly know individual tortoises by name and can estimate ages by shell size and surface texture patterns that casual visitors cannot read
  • Prison history context — the story of a slave prison that never imprisoned anyone connects to the broader history of the East African slave trade that Stone Town's Anglican Cathedral memorial also addresses
  • Marine ecology — a guide who accompanies snorkelling excursions can identify coral species, explain bleaching impacts, and point out species camouflaged against the reef floor that independently snorkelling visitors swim directly over
  • Tidal timing expertise — knowing which snorkel area has the best visibility at the current tide state, and which rocks shelter the most diverse fish communities, is experiential knowledge that maximises a short reef visit

Tips for Visitors

Bring sunscreen and apply it before the boat crossing — the 20-minute open-water passage offers no shade. Do not sit on or ride the tortoises; they can live to 200 years and are irreplaceable. Bring a small amount of cash for the entry fee and the restaurant — card payments are not reliably available on the island. The crossing can be wet in choppy conditions — pack your phone and camera in a waterproof bag. For the best photographs, visit early in the morning when the tortoises are most active in the cooler temperatures and the light is soft and warm. Combine with a morning in Stone Town — the Forodhani Gardens waterfront from which boats depart is also the site of the evening food market, creating a natural bookend to a full Zanzibar day.

Frequently Asked Questions

How do you get to Changuu Prison Island?

Speedboats depart from the main waterfront jetty in Stone Town, a 20-minute crossing across the clear channels between Zanzibar and the small island. Boats are arranged through guesthouses, tour operators, or directly with boatmen at the jetty — agree the price before boarding and confirm it includes the return journey and waiting time. The crossing is calm in the dry season from June through October and in January and February; the wet season can make it rough.

Can I snorkel around Changuu Island?

Yes — the shallow coral gardens surrounding the island are among the most accessible snorkelling sites near Stone Town, with good visibility in the dry season revealing hard and soft coral formations, parrotfish, angelfish, and occasionally small reef sharks. Most boat operators carry masks and fins for hire or include them in the trip price. The best snorkel window is at high tide when water clarity peaks over the reef flat.

How old are the giant tortoises on Changuu?

The oldest individuals are estimated at 130 to 150 years, placing their hatching dates in the 1870s to 1890s — well before the island's prison was built and before the First World War. The tortoises were a gift from the Governor of Seychelles in the early 1900s; the original population has grown to around 100 individuals through breeding on the island.