“It’s like being in another world!” may be the most predictable observation following a close encounter with the Great Barrier Reef, but it’s only when you’ve come face to face with the extraordinary animals, shapes and colours here that you realize you’ve truly entered a watery parallel universe. And as a curious thick-lipped potato cod nudges your mask, you might also wonder, “who exactly is watching who?”

The Great Barrier Reef follows Australia’s continental shelf from Lady Elliot Island, in southern Queensland, 2300km north to New Guinea. Its northern reaches are closer to land, so while it’s 300km to the main body from Gladstone, Cairns is barely 50km distant, making this the best place for reef day-trips. Scuba diving may get you more quality time down below, but a well-chosen snorkelling location can reveal marvels no less superb without all the bother of training, equipment and lengthy safety procedures. Though commonly called the world’s biggest life form, the Great Barrier Reef is more an intricate network of patch reefs than a single entity. All of it, however, was built by one animal: the tiny coral polyp which grows together to create modular colonies – corals. These in turn provide food, shelter and hunting grounds for a bewildering assortment of more mobile creatures.

Rays, moray eels and turtles glide effortlessly by, while fish so dazzling they clearly missed out on camouflage training dart between caves to nibble on coral branches, and slug-like nudibranchs sashay in the current. It all unfolds before you one breath at a time, a never-ending grand promenade of the life aquatic.

For more information, visit www.greatbarrierreef.aus.net. For snorkel tours, try www.seastarcruises.com.au.