The most incredible day unfolded for us, in a secluded bay on a secluded island, off the coast of Coromandel on Sunday. Waking up in Coralie Bay is always special, but we had no idea what was in store for us.

A small pod of nine dolphins surrounded the yacht at daybreak and were ready for a full day of action.

A handful of other boats cleared out to go fishing or cruising, leaving us – two people, nine dolphins and one dog, to play all day together in the pristine waters of the bay.

As do many boaties, we've had a lot of dolphin encounters over the years, many times around the Mercs and beyond, including some tragic tales too – such as re-floating a stranded pod on the remote Karikari Peninsula in the far north; and solving the disappearance of Moko in Tauranga.

However, this week's experience was completely different again. These wild creatures chose to play around our boat and with us in the water. Not just a chance, brief encounter but a whole day, from daylight till dusk.

Even Flo, the water-mad Labrador, was part of the action, swimming out amongst them and at times surrounded by circling dolphins as they cavorted in the shallows.

The cameras clicked and the video rolled, as Claire jumped in with mask and underwater action cam.

Soon we were all in, filming, amazed at how these massive creatures, some up to 4 metres, would whoosh up, circle around and stay swimming within touching distance of us ungainly humans.

It seems the dolphins were there for a specific purpose, and as the day wore on the antics became more suggestive and ritual. Constantly they were picking up seaweed, loose kelp from the sea floor, and carrying it on their noses.

Then they'd let it slip onto their dorsal fins and parade around the bay. The others seemed to be following the one with the weed. We joked that it seemed like some sort of wedding dance.

'Darling, does this seaweed make my tail look big?”

The courting continued in the shallows till sundown.

The experts tell us the seaweed game is a part of the courtship ritual. The male can spend quite some time selecting a quality piece, swimming around with it on his fins and tail, before offering it to the prospective female. If he's impressed her, she'll pick it up and adorn her fins with it.

Apparently, all signals of acceptance. Not unlike a bloke giving a girl a bouquet of flowers. The courtship can take hours, but when they get down to the act, the actual rumpy, pumpy can be over in seconds.

In Coralie we watched in stunned amazement as the amorous intent of the foreplay gave way to some full-on mating and we wisely decided to give them their intimate time and space. Extracting ourselves from this fishy fornicating, we carefully swam back to the boat, trying not to look too appealing, in a fishy kind of way.

The pod carried on carrying on, vigorously all day, right alongside the yacht and in the shallows of the bay.

Dolphins mate belly to belly and we'd see flashes of silver undersides steam around, with a couple of keen suitors in hot pursuit. Blobs of bright yellow dolphin ejaculate speckled the water.

Forget the fishing and diving today, this was all too fascinating to tear ourselves away.

In the late afternoon, the mood seemed to change and there was a lot of spy-hopping and bobbing going on. Some leapt gently and flopped down repeatedly on their backs.

As the sun set behind Great Mercury in a blaze of crimson and orange, the dolphins were still going strong as we had dinner and turned in, exhausted.

The next morning, another perfect day in a perfect bay and the pod came loping back into the bay. Presumably they'd been out for a night hunt, but it seemed they were back to the beach for more shenanigans.

This family was thrilled to find dolphins swimming around them in the shallows.

The crew of the launch Sinbad were treated to a display of aerobatics.

The seaweed game is apparently part of the courtship rituals.