‘On the high seas in Tonga, we are honking along at 8 knots, sailing to the most distant island in the Vava’u archipelago, Eueiki.

This is our beautiful catamaran, Thalassa, having reached Eueiki.

We are visiting Tonga in August, to swim with the humpback whales as they migrate from Antarctica to the warmer waters, to birth their calves.

It would be hard to find a better place to snorkel and explore the ocean.

It is our first morning and there is high excitement as we spot a whale close to the boat. While I fumble for my camera, it breaches in front of us exposing its white and indigo belly before flicking its tail and descending deep into the water. Disappointed, I’m sure I have missed a moment in a lifetime, but it does it again.

The indigo belly of one of the world’s finest creatures.

This was the beginning of a week of whale watching.

Tonga is one of the very few places in the world where it is possible to swim with whales. Needing a certified guide to swim with these beauties, we hire Alan for the day, a scruffy, bearded Kiwi. He says he has been getting up close with whales for 23 years and believes they know him.

Alan, our skipper gives us a briefing about respecting the whales, especially mothers that have calved.

Cruising around the Vava’u archipelago we spot a whale and Alan gets as close is allowable, without infringing on its space.

Four of us get in the water with goggles, snorkels and flippers and swim towards the whale as she slowly begins to descend.

Returning to the boat after a close and moving encounter with a mother.

Feeling completely overwhelmed alongside this incredible 40-tonne mammal, we eye each other up. She doesn’t seem to mind my curiosity and I feel a flicker of emotion for this mother-to-be with her barnacle-encrusted head and parasitic fish clinging to her back.

In our next encounter, we sidle up to a mother who has already calved. We are warier as we know she will be protective of her offspring. We see the calf and can’t help notice its smooth black skin, unlike the bumps and barnacles on its aged and wise mother.

Graceful and huge, they earn their respect.

Alan says the young calves drink 100 litres of rich milk a day, gaining an unbelievable 3-5kg an hour at their peak. Meanwhile, the mother loses condition, not eating until they migrate back to Antarctica where she will feast on krill.

Drying off, back on the boat, there is little time to rest. Alan shouts, “There’s a heat run on.” With that, we are off again in dogged pursuit of more whales.

Alan spots more activity 400m away as the whales “blow”. Surfacing, they exhale air through their blowholes creating a light mist of water vapour, giving their location away. Several bulls are pursuing a female.

From afar we can see the mist from the whales blowholes.

There are restrictions about pursuing the whales and Alan feels we have had a fair share and we agree. He delivers us back to our catamaran. We are not only much better informed about humpback whales but we have experienced what most people only dream about.’