At 9.46am on Sunday, February 7, Carl Gerrard dropped his phone in the Clutha River, Wānaka, while he was floating down it.

Two months later, at the beginning of April, Rebecca Kinaston and her partner Graham were visiting Wānaka and decided to go for a snorkel in the river when they spotted the phone, inside a plastic bag.

She explained the couple were in Wānaka at the start of April to see family and attend the Wheels at Wānaka event. They decided to stop near the Albert Town campground and decided to go snorkel in the river.

"We like to go snorkelling and look at the trout cos the water is so clear," she said. While they usually only find rubbish and the occasional fishing lure, the bounty was different that day.

Rebecca and her partner Graham often go snorkeling and diving together. Photo / Supplied

"It was in a plastic bag so we thought it was just another piece of rubbish," she added.

They took it home to Waitati, near Dunedin, and Rebecca hoped she could dry it out and get it working again. The 35-year-old bioarcheologist is used to retrieving bones - usually human ones - from land. But it turns out she's also quite good at recovering smartphones that have been deep in fresh water for quite some time.

She's kept the phone in her living room, giving it time to dry before she tried plugging it in. A good month had gone by until, earlier this week, she had a dream that she tried plugging the phone in to charge and it had started working. So she woke up and decided to do exactly that.

Much to her surprise, the phone screen lit up as she turned it on and a photo of a dog appeared on it.

Rebecca Kinaston turned the phone on a month after finding it and, much to her surprise, it was still working. Photo / Supplied

Amazed the phone was still working, she decided to join the local Wānaka group on Facebook and post a photo of the phone, in the hope of finding its rightful owner.

"This is a wild story! My boyfriend and I were snorkelling the Clutha and found this iPhone (8?) at the bottom of the river near the Albert Town Camp Ground on April 4th," she wrote in the Upper Clutha Community Notices Facebook group.

"It was in a Budget Rental Car bag. I dried it and plugged it in and it turned on today! It appears to have been lost on Feb 7th in the morning, probably by someone floating or kayaking the river. We would love to get the phone back to its owner. Does anyone recognise the brindle dog with a blue collar and red tag?"

No one recognised the phone but the dog in the phone's background image, it tuns out, was a bit of a local legend in Wānaka.

Thanks to late Magnum, a German Shorthaired Pointer who died three years ago, it took less than an hour for someone to tag Carl Gerrard in the post, letting him know his phone, which he had dropped in the river three months earlier, had been found and was still in working order.

"Oh my god. This is truly amazing. This is my phone we lost it almost 3 months ago whilst floating down the Clutha. This is a picture of my late dog Magnum. I know the password for the phone. Truly amazing and well I am speechless," he wrote.

Speaking to the Herald, Carl said he was having a quiet Friday evening in with his wife, drinking a glass of wine and watching a movie, when he saw the Facebook notification that he had been tagged in the post.

"At first I didn't even notice the phone, I was just trying to understand why I'd been tagged in a post with a photo of our old dog that we all loved so dearly," he said.

Magnum was "a bit of legend" around Wānaka. He would often roam around and was well known and loved by many, getting frequent pats from the locals at Kai, the cafe on the lakefront, and even sometimes getting on the dancefloors of the bars in town late at night, with Carl getting woken up with calls to go get his dog, only to find him happily hanging out with the bouncers.

Carl Gerrard and his dog. Photo / Supplied

With that kind of legacy, it's no surprise Magnum played such a big part in reuniting his owner with his lost posession.

The man, who lives in Wānaka with his wife and children and works as a builder, often goes floating down the river, just like he used to, with Magnum on the board.

"We float down the river regularly and have done it at least three or four more times and I have been more vigilant than normal," he said. Usually he looks for lures - "they're about 25 bucks each!" - but, since then, he's also kept an eye out for his phone.

However, he never really expected to find it. "The luck I would need would be multiple millions to one, so I stopped looking."

The phone was in a cheap dry bag, "one of those you get for free when you rent a car in Europe in summer", and was found about 3.5km down the river from where Carl dropped it in February.

When asked about arrangements to pick up the phone from Rebecca, who lives nearly 300km away, Carl offered yet another incredible detail about this story.

"Well ... it turns out she actually lives 200 metres away from my childhood best friend in the UK, who was also the best man at my wedding. I'm 46 years old and I've known him since I was 3. It was almost returned to me because we are basically the same person, that's how close we are," he said.

Rebecca is stoked to get the phone back to its owner.

"I just love returning things to people, it makes their day," she said.

As for Carl, after receiving advice from multiple friends on this, he is off to buy a lotto ticket.