The chugging of the converted fishing boat stops and the world is silent. The palm tree-lined coast of the Indonesian island is hundreds of metres away.
Although the reef edge is near, the water where we hover is 100m deep. The captain gestures to my family to jump off the boat. I wonder if this is right.
"What, here?" I ask. "Yes here, Turtle City," he grins.
My trusting four-year-old daughter turns her wide eyes up to me. I flash her a smile and, together, we plunge into the bottomless blue.
Immediately, my sons, aged 11 and eight, are squealing through their snorkels.
Right below us swims a 2m-long green turtle. Sunlight bounces off the ancient creature's shell in every direction. The behemoth seems to fly as her front flippers haul her through the water. She is unafraid and, soon, we cannot keep pace and watch her glide into infinity.
The clarity of the water is breathtaking and I see several more turtles - to the left, right and far below.
Silkair flies direct from Singapore to Manado in Indonesia four times a week.
Hotels can arrange an airport pick-up to Bunaken Island. It is a 40-minute drive from the airport to the port of Manado. Your hotel boat will meet you for the 40-minute boat trip to the island.
I stay at Bunaken Cha Cha Nature Resort (www.bunakenchacha.com). Room rates start at $175 a person a night.
It takes about two hours by car from Manado to Tangkoko Batuangus Nature Reserve. Accommodation is basic. I stay at Dove Villas (tel: +62-813-5624-5160) and it costs $26 for a double room, including breakfast. The very friendly owners, Ouldy and Evi, can arrange forest guides and transport to and from anywhere in the region.
From Tangkoko to Tomohon, it takes about two hours by car. There are several hotels in Tomohon and I choose Highland Resort and Spa (www.highlandresort.info). Rates start at $35 for a double room.
It takes about one hour to drive back to Manado airport.
• If you are snorkelling with children, pack good quality equipment for them. Resorts can supply equipment for adults, but often do not stock many sizes for children. Quality gear will improve their experience - everyone is happier when masks are not leaking.
• When visiting Tangkoko Batuangus Nature Reserve, you will need long sleeves, long pants and insect repellent for protection against tiny biting bugs. Have a torch for the dawn and dusk trips.
• Although the dive resorts at Bunaken Island are very comfortable, truly high-end luxury in north Sulawesi is uncommon. Adjust your expectations for the rustic conditions and sometimes slow service, particularly around Tangkoko.
GATEWAY TO MARINE PARADISE
The island of Sulawesi lies 600km north-east of Bali. I have flown from Singapore to Manado in Northern Sulawesi, intending to show my children the wild highlights of this zone.
In the next nine days, we will be immersed in the underwater paradise of Bunaken Island, encounter monkeys in the Tangkoko Batuangus Nature Reserve and enjoy the volcanic highlands of Tomohon.
Emerging from the airport, we take a 40-minute drive to Manado Port, the gateway to Bunaken and other islands.
I am eager for our adventure to begin but, at the port, I notice with great dismay that the water is bobbing with plastic. I find it astonishing that this polluted harbour is the gateway to a natural paradise.
The wooden boat we will take to Bunaken Island is filled with bags of rice, crates of vegetables, beer, crew and, lastly, my family. Once underway, the garbage of the port lessens and my eyes are soothed by mountainous, green views of the mainland.
The island of Manado Tua is prominent on the skyline, with its ancient volcanic slopes. Our boatman says: "That flat one beside it - that's Bunaken Island."
These islands are part of the Bunaken Marine Park.
We are in one of the most diverse coral reef ecosystems in the world, with approximately 2,000 species of tropical fish and 390 types of corals so far recorded from the area. There are still infringements of the fishing rules here, but on the whole, the reef is pristine.
I am face to face with a resting turtle, safely wedged into a small crevice in the reef wall. My hand wants to touch the smooth shell, but I stop short. It is not my place to disturb this wild, sleeping beauty.
Arriving at Bunaken Cha Cha Nature Resort (www.bunaken chacha.com), I pick my way through the shallows of the reef flat to the hotel. My son finds a better way, getting pulled along on a wooden raft with the luggage.
Like most hotels on Bunaken Island, it is very personal, accommodating a maximum of 20 guests.
My family has two beachfront rooms, featuring natural materials and open-air showers. A shady verandah joins our rooms and, as I enjoy the view, the ocean beckons.
MYRIAD OCEAN COLOURS
On my first snorkel from the beach, I encounter a green turtle followed by a skittish whitetip reef shark. Reef fish of orange, blue and pink cloud my vision and it feels like I am in an aquarium dream.
I am inspired to dust off my dive certification and go out with a scuba tank.
Sitting on a boat in dive gear for the first time in 12 years, I am sightly nervous.
The in-house divemaster is a local from Bunaken and a man of few words. However, under the water, he conducts my refresher course with confidence, then proudly leads me through his shimmering backyard.
Gently parting some rubbery soft coral, he shows me the tiny, delicate orangutan crab. No bigger than the nail on my pinky, its orange "fur" sways with the current.
A metallic "tap, tap" on the divemaster's tank prompts me to look straight down.
About 15m below me, a 2m-long blue and green Napoleon wrasse darts upwards and flashes back down, followed by the sleek and silvery body of a shark.
The two dance aggressively and, as I watch, I am astonished to see a 1m-long giant trevally glide over to check out the action.
Tap, tap again, and I am face to face with a resting turtle, safely wedged into a small crevice in the reef wall.
My hand wants to touch the smooth shell, but I stop short. It is not my place to disturb this wild, sleeping beauty.
MONKEYS WITH MOHAWKS
Dolphins accompany my boat as I bid farewell to Bunaken Island and, when they finally slide away into the glassy expanses, I turn my thoughts to the wild animals of the land.
I have read that Sulawesi and the neighbouring island of Borneo have been separated by deep water for more than 50 million years. An imaginary line was drawn between the two in 1859 by naturalist Alfred Wallace and is thus named the Wallace Line.
The animals on either side of the line are quite distinct, with only a few successfully crossing the line. Many native animals unique to Northern Sulawesi are still found in the forests and these are only a two-hour drive from Manado.
Emerging from my mosquito net at 4am the next morning and stumbling into socks, trousers and long sleeves for insect protection, I hope it is worth the effort.
My torch lights the track as I follow our guide deep into the forest.
Shushing excited kids, I am surprised to hear leaves rustling and see shadowy figures up ahead.
A troupe of macaques is travelling in the same direction as us and, as the sunrise starts to penetrate the forest, they are suddenly, eerily, all around us.
The black crested macaque is one of 127 species of mammals found in Tangkoko Batuangus Nature Reserve. Still hunted for bush meat and threatened by deforestation, the monkey is critically endangered and lives only in Northern Sulawesi.
There are about 40 macaques in the group we are with, all with a distinctive black mohawk style.
Males squabble, chase and wrestle, showing off to females. Mothers piggy-back their babies and munch on bugs they pull from one another's fur. Rowdy adolescents jump from branch to vine before scampering across the forest floor in play.
I am thrilled to note that our presence is ignored. These macaques are living a naturally wild life, unaffected by the humans observing them.
Needing to see more, I return later that night for a second guided walk. This time, I am seeking the world's smallest monkey - the tarsier.
Creeping through the dark jungle, I am quickly rewarded by our guides' local knowledge.
The tiny furball is perched on a branch, having emerged from its daytime refuge.
It is impossibly cute, with enormous eyes, and I laugh as my daughter whispers: "Mum, can we get a tarsier?"
Before we exit the park, Tangkoko has one more surprise for me. The driver stops suddenly by the side of the road. Our guide bounds out of the car, pointing. "Look, tarantula," he says.
I gaze with awe at the hairy, menacing, dinner plate-sized predator and I am wondering if this is a prank.
But as it stretches one leg towards me, I am back in the jeep before you can say: "It is a real spider."
VOLCANOES AND BUSH RAT KEBABS
It is a two-hour drive from the nature reserve to Tomohon in the Minahasa Highlands and volcanic peaks and photogenic lakes entice hikers.
With the family in tow and limited time, I am not hiking, but taking a 6.30am stroll, savouring each breath of the chilly mountain air.
The mist clings to the edges of the simmering volcano, Gunung Lokon, as I watch intrepid tourists begin the four-hour hike up its slope. Other groups are driving to Gunung Mahawu volcano or to view the changing colours of the sulphuric lake, Danau Linow.
My last morning is spent at the infamous Tomohon market. Traditional Minahasan culture is alive here and the foods on offer can be somewhat confronting.
I move my children quickly past the dog section and feel very squeamish about the bats and whole bush rat kebabs. The gory sights and pungent smells mean I am slightly overwhelmed by the time I rejoin our car for the one-hour drive to the Manado airport.
It is not my intention to judge the traditions of the Minahasans. But the experience makes me realise how much I value the wild animals and hope Sulawesi continues to protect its unique wild treasures for generations to come.
• Carolyn Beasley is an Australian freelance travel and environment writer and a marine scientist based in Singapore.