SNORKELLING in the sandy channel between Low Island and Woody Island, I came across a long piece of rope, laid out along on the sea floor.
It took me a few seconds to realise I was actually looking at the tail (and barb) of an enormous stingray, casually lying there camouflaged in the white substrate.
It's not recommended snorkelling above stingrays, but there was really no cause for alarm.
It seemed the ray was far more content to remain sitting there minding its own business, as much as I was exploring the depths surrounding one of the Great Barrier Reef's most historic offshore destinations.
Low Isles, 15km off the coast of Port Douglas, is one of the best places to experience the reef in all of its glory.
The isles consists of the two islands: one uninhabited and full of mangroves, and a smaller island which is a sandy coral cay with a small forest and large lighthouse.
The view of the cay, Low Island, when you are sailing in from Port Douglas on-board Quicksilver Cruises's catamaran Wavedancer, is almost a dreamscape: crystal-clear blue water, a white sandy island, emerald vegetation and then this beautiful white lighthouse capped with a bright red roof.
You almost feel like staying on board the vessel and painting the stunning view.
But you don't, of course, because the water beckons.
Once you are ferried to the beach, you strap on a snorkel and flippers and zoom around the shallows.
The moment I plunged into the water, I encountered two small blacktip reef sharks, bolting after a school of fish.
The predators were no bigger than my forearm, and I felt completely at ease being a casual observer.
Large, healthy-looking boulders of coral had hordes of reef fish buzzing around them, tending to algae and other morsels of food.
And crevices hid some of the reef's more shy critters, including a small mottled octopus.
Towelling off after a dip, there is a short walk around the sandy island, which takes a total 15 minutes, but you can spend a lot longer just reading the extensive history of the reef locality.
Captain James Cook discovered Low Isles in 1770, describing it in his log as a "small low island".
Since then, the tiny piece of land and its 22 hectares of coral have played an important part of history, maintaining weather records since 1887, becoming the base in 1928 for a year-long scientific survey which studied the structure and ecology of the surrounding reef.
This study was the first detailed research of a coral reef anywhere in the world.
Many current theories of coral reef are based on the findings of this expedition.
The lighthouse, which was first lit in 1878, still has caretakers today.
If you join the Low Isles Preservation Society, you can sign up as a volunteer to take over duties whenever the caretaker is away on holidays.
Not that you imagine this happens much - it would be difficult to imagine anyone wanting to escape this idyllic slice of paradise.
The writer was a guest of Quicksilver Cruises.
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