On the northernmost tip of Unguja, the island known as Zanzibar, is Nungwi village, a long-time favourite among backpackers and now offering some smarter accommodation. Ras Nungwi Beach hotel has the best location; its comfortable makuti-thatched villas are adjacent to wild bush and a long white swathe of sand.
The hotel's dive shop is run by Zanzibar Watersports. If, like me, you don't dive, a day's snorkelling on nearby Mnemba island is the next best thing. The sea snakes and stonefish, multi-coloured shoals and outlandish corals were mesmerising – and for good measure, a pod of dolphins buzzed the boat on our way back to shore.
The firm also arranges parasailing and jet-ski safaris – and deep sea fishing.
I've always connected deep sea game fishing with Hemingway – and bravura levels of testosterone. Yet it was the expectation that snagged me. What would we catch?
Skipper Abi welcomed me aboard Timimi, a stocky white fishing boat bristling with rods. Our destination was Leven Banks, an area of ocean halfway between Unguja and Pemba. I spent hours before I got a bite. Under Abi's expert supervision I reeled in a splashing 14kg wahoo, iridescent black-blue and stripy – an exhilarating induction.
But adventure in Zanzibar isn't exclusively aquatic. Getting lost in the capital, Stone Town, a World Heritage site, is a heady experience. The labyrinthine alleys are riddled with smells, tastes, shadows and whispers.
The sense of disorientation takes some getting used to, but the rewards – a wonderful fish and spice market, secret squares, Zanzibari carved-doors and some exquisite Omani architecture – are well worth seeking out.
I sought respite at Emerson Skeens' eponymous new hotel, Emerson Spice. The proprietor helped put Zanzibar on the tourist map by introducing the boutique hotel concept to the island. His latest incarnation is effortlessly stylish, with suites bedecked with Zanzibari beds, scumbled azure walls, and vast serpentine baths. It's an intoxicating mixture of Omani merchant house, grand opera and Babylonian garden.
From Emerson's rooftop restaurant, it's just about possible to make out Chumbe Island. This small dot in the ocean was for years an out-of-bounds military base – the upshot being a virtually pristine marine environment that was officially gazetted by the Zanzibari government as a conservation area in 1994. Accommodation is simple; not much more than glorified bandas or thatched huts. But it's gorgeous.
Most of the island is covered in dense tropical thicket and dominated by a Victorian lighthouse. I climbed it for a spectacular sundowner; after 131 steps the welcome breeze momentarily blew the intense fug of heat away.
By the time I'd got back to the shore, the sun had vanished, encouraging some of the island's rarer inhabitants to emerge, including endangered coconut crabs. A ranger pointed out a tiddler: the size of a blue armour-plated football, wielding claws to crack open coconuts. I was mindful of my toes.
However, I was keen to get back on the water. And it was to be no ordinary yacht for me; I'd got my eye on an ngalawa. This traditional fishing boat is the granddaddy of the hydrofoil and shouldn't be judged on looks alone. Head ranger Omari took me out for a spin, expertly putting the boat through her paces. The smallest draught sent us scudding at an exhilarating rate, creaking and lunging over swells.
I joined Omari again for an afternoon sea safari. Here I encountered a hawksbill turtle in the neon and chrome corals; he eyed me disdainfully before flapping languidly off.
Misali Island, sitting off the south west coast of Pemba, is another marine reserve, but has a strict day-trips-only regulation. It's an idyllic base for diving and snorkelling.
Luxurious accommodation can be found at Fundu Lagoon hotel immediately opposite on mainland Pemba. The creation of fashion designer Ellis Flyte, Fundu ticks all the sybaritic boxes. Thatched safari-style tents are dotted throughout the vast hotel grounds.
I'd anticipated an afternoon of snorkelling off Misali, but Filbert, Fundu's resident dive master, had other ideas. It took much cajoling, and for Filbert to talk me through every detail, but he eventually persuaded me to try a "discover scuba" course. My anxieties disolved when I saw kaleidoscopic marine life from a new perspective.
Later, Rusty, Fundu's man with the rods, asked me to join him on a fishing trip. His blinding white boat was the business. No sooner had we put out lines than a fish came arcing out of the water. A dazzling streak of gold, silver and Wedgewood-blue pounced: a dorado. The ceviche back at the hotel that evening couldn't get any fresher.
I decided to spend my last evening cruising on a traditional dhow. Mama Casa is majestic. When her single sail is hoisted and catches the breeze, she comes to life. Her simple, crude construction creaked and shifted in the roll of gentle waves and I drifted off... it seemed that, finally, my Indian Ocean adventure had got the better of me.