A search is underway for the rightful owners of a GoPro camera lost at sea five years ago, after it was found nearly 30 feet underwater on the Great Barrier Reef.

American tourist John Michael Darrin discovered the damaged device while diving off the far north Queensland coast in November 2017, but only recently managed to retrieve the near-300 photos and a couple of videos from it.

Among the many photos were selfies of a man and woman from 2013, snorkelling in the very waters where the gadget was found.

Mr Darrin has turned to Facebook and Reddit to share the photos and spread the word to try and return the long-lost camera.

"I found it about 30 feet below the surface, tucked away on a coral reef without a case," Mr Darrin told ABC News.

"When I grabbed it, it was covered in a red algae and other sea life … strong hints that it's been down there for a while now."

The GoPro was found damaged beyond repair. ( Supplied: John Michael Darrin )

Mr Darrin said the battery had imploded and there was little hope the micro SD card would work, but he was determined to get it out.

"All the corrosion and overgrown sea life impacted the SD card, so it took some force and TLC to make sure I didn't damage any of the readers," he said.

It took him hours, and when he got it free, the metal pins were covered in "hard, white gunk".

A couple of the GoPro's photos have been shared online in the hopes of identifying the owners. ( Supplied: John Michael Darrin )

Retrieved SD card goes missing for another year

Ironically, Mr Darrin would go on to lose the SD card himself for almost a year.

The day after discovering the camera he was on a plane to Bali, and upon arrival was unable to find the SD card he had worked so hard to retrieve.

"It wasn't in my backpack, or my GoPro case, or my little bag of SD cards. I couldn't find it anywhere," he said.

"I checked and checked, all throughout the next couple of months as we backpacked through Thailand, Vietnam, and Hong Kong, hoping it would show up.

"But no luck. I was completely bummed."

This past week, nearly 12 months on, the card turned up.

The SD card contained about 300 photos. ( Supplied: John Michael Darrin )

"I'm going through old stuff and begin packing for a dive trip coming up next week, [and] as I'm pulling stuff out and rearranging things, out falls the SD card," Mr Darrin said.

"I instantly got so excited, and the same adrenaline I had when I first found it came rushing back."

Using isopropyl alcohol following a tip from Reddit, he was able to gently rub the gunk off the SD card using a toothpick.

"I dry it off and push the card into a reader and insert it into my computer. My computer beeps, and instantly reads the card," he said.

"As I waited in anticipation, what was a couple of seconds felt like forever.

"I open up the files and instantly go through the footage, looking for anything that could help me find them. This whole process took a almost a year to solve."

Mr Darrin said there were a few details he could pull from the camera. He said the couple appeared to be on a snorkelling tour on board the Cairns-based Rum Runner in January 2013.

"I've lost a GoPro myself, so I understand their feeling. I'd hope someone would try to return it as well," he said.