Pemba is about half as big as Unguja, Zanzibar's proper name. Together, these islands form the Zanzibar archipelago. It is technically a semi-autonomous region of Tanzania, and officials unnecessarily stamp your passport when you travel between Dar es Salaam and Unguja's Stone town, perhaps harking back to a day when Zanzibar was independent from Tanganyika.

Pemba boasts a rare 'megabat', the Pemba Flying Fox, endemic to the island and with a wingspan of 1.6 metres. I saw them in the northern town of Wete, my favourite place in Tanzania. The rooftop terrace was part of Sharook Riviera Grand Lodge, but anyone can see these bats as they fly at dusk, from their nesting grounds close to the harbour to their feeding grounds to the north, and back before dawn.

Close to Wete's harbour is the fish market, where a crowd gathers on the dark beach sand in the mornings, looking, assessing the fish at their feet and bargaining. One at a time, the line fishermen drag their catch from the boats, onto the wet sand.  Money changes hands at the water. Behind the crowd, the fish are cleaned and quartered. Tuna are sliced into two, with part of the tail and part of the head in each half. The fish pieces are placed on trading tables or loaded onto baskets. Sometimes, whole sailfish are carried across a shoulder to a waiting bicycle. They look heavier than the man carrying them, longer than the length of the bicycle that is to transport them.

Fish, fishing, and tourists who come to see fish, drive Pemba's economy. While Zanzibar has spectacular beaches, Pemba has world-class diving and snorkelling. To the west of Wete is a huge lagoon, the bay protected by Fundo island and Njao island. Between these islands are small gaps where the tides push nutrient-rich water in and out. I managed to hitch a ride on a dive boat and when I jumped off the boat to snorkel in shallow water, about two metres deep, the tropical aquarium fish filled my vision. Big round corals almost reached the surface, and tiny fish were hiding in every gap, swimming around and over this coral as if it was their whole world, a tiny planet submerged in shallow water. And another, only a few metres away. I inched through the water from one coral to another, one planet to another, until suddenly the ocean floor just disappeared, and I was swimming over the edge of a cliff. Dark, deep water staring up at me. That was where the divers had gone, exploring this vertical world. I could see bigger fish, living in ledges and crevasses on the cliff. I took a deep breath and plunged, diving along the cliff and into the dark blue deep.

After a stop at a second site, like an underwater mountain, we stopped for lunch. There are so many hidden little beaches, we took our pick.

It can be difficult for a backpacker to access remote areas in Pemba. For example the islands, the  isolated little beaches, the dive sites, the mangrove forests. There are expensive tours offered by expensive resorts, and there are the local fishermen who can be paid to act as ferries and guides, but they will explain that this will mean they are not fishing, and will charge a decent sum. There are not many options in between. I recommend finding a boat that can be rowed or paddled, and hired for the day. Pemba has a strong bargaining culture, and not many poor tourists. A basic grasp of the kiSwahili language, in particular the numbers, and a good idea of what a fair price is and how much you are willing to pay, is essential before negotiations even begin. Asking a friendly English-speaking local to help is possible, but in all likelihood he will try to get a cut, a finder's fee. This is a poor region in a poor country, which relies heavily on tourism, so everyone has one eye on the tourist trade as a way to earn a living. Once a fee is negotiated and the bargaining is over, then everyone lets their guard down. 

Tuna are sliced into two, with part of the tail and part of the head in each half. The fish pieces are placed on trading tables or loaded onto baskets. They look heavier than the man carrying them, longer than the length of the bicycle that is to transport them. 

The myriad resorts of Zanzibar may be good for the country's GDP, but many locals feel cheated. Some stretches of beach are fenced off, inaccessible to the people who have lived there all their lives. 

I made lasting friends in Tanzania, and met some of the friendliest people in Pemba, most of who wanted something from me at first but relaxed once business was done. The owner of the hostel where I stayed, a gentle old man called Mzee Sharook, owned a fruit farm to the north. He came to me every morning with freshly pressed juices and exotic fruits for me to try. Breakfast was always fruit. And he seemed to take great pleasure in giving me something I had never seen before. A beautiful old man with a dazzlingly wide smile, broken teeth, and a warm heart.

Pemba also boasts some of the extraordinary white sandy beaches that make Zanzibar so popular. The easiest to access is Misali Island. Ferries go there from the capital of Pemba, Chake Chake. It is also possible to hire a local motor boat from the harbour. As usual in Pemba, it's best to have an idea of the price beforehand, and to bargain hard. But not too hard. Petrol is expensive, after all.

When I was there with a group of young Russian backpackers, we were the only tourists on the entire stretch of pristine white sand, with no development as far as the eye could see, no hawkers, no activity of any kind. Just white sand and warm turquoise water filled with colourful fish. One friend was quick to remind me that this beach was not as good as another we had visited, Mbuyuni beach in the north-east. Her reasoning: the sand was finer on the first beach.

Accessible only by hired car, Mbuyuni beach is a huge stretch of, I must admit, extreme beauty and very fine white sand. We had gone there with a group, bought some fruit from some locals, and swam in the shallow pools. The waters of Mbuyuni form a lagoon. As we ate fresh fruit on the beach, totally relaxed, we could see the edge of the coral, about a kilometre out to sea, where the waves were breaking and some locals were gathering seafood. Not all locals were friendly, however, and some villagers strongly asked us to turn around before we got to the beach. They were afraid that if tourists came to their beach, development would follow. The myriad resorts of Zanzibar may be good for the country's GDP, but many locals feel cheated. Some stretches of beach are fenced off, inaccessible to the people who have lived there all their lives.

We defused the situation by explaining that we were backpackers, cheap students looking to get lost in the world. To get stuck in local daladala taxis, next to bright yellow buckets of the tiny fluted-mouthed fish we had been snorkelling with just hours earlier. To eat local food, from the delicious seafood and fresh but alien fruit, to the strange dried octopus. And to meet local people. Pemba has a rich history of trade dating as far back as 600AD, stretching as far as China. Its people are Swahili, Omani, Shirazi. The culture seems more conservative than Zanzibar's, but it is fascinating and unique. The people want to guard their island, and it is easy to see why. The Green Island is an unsung paradise.