MICHAEL WALSH FORMER MARINER: The vast oceans and seas that touch all of our lives abound with mystery. The fathomless and mysterious oceans consist of ever-changing horizons hardly touched by human hands. Mysterious because we know more about the distant moon than we do of the enigmatic waters we look over and sail across.

The world’s multitude of seas cover 70 per cent of the earth’s surface. To say the seas are vast is a gross underestimate. 80 per cent of the seas we never see is below the surface. Our world is a marine planet and we humans occupy less than 30 per cent of it. We don’t treat the fraction we occupy very well, do we?

Despite its size and impact on the lives of every organism on Earth, the ocean remains an impenetrable enigma. More than 80 per cent of the ocean has never been mapped, explored, or even seen by humans. A far greater percentage of the surfaces of the moon and the planet Mars have been better mapped and studied than our own ocean floor.

Although there is much more to learn, oceanographers have already made some amazing discoveries. For example, we know that the ocean contains towering mountain ranges and deep canyons, known as trenches, just like those on land. The peak of the world’s tallest mountain, Mount Everest in the Himalayas, measures 8.84 kilometres (5.49 miles) high, They wouldn’t even break the surface if it were placed in the Pacific Ocean’s Mariana Trench or Philippine Trench which are two of the deepest parts of the ocean.

The Atlantic Ocean is relatively shallow because large parts of its seafloor are made up of continental shelves, parts of the continents that extend far out into the ocean. The average depth of the entire ocean is 3,720 meters (12,200 feet). It is unknown how many different species call the ocean their home. With many marine ecosystems suffering from rising sea temperatures, pollution, and other problems, some oceanographers believe the number of species is dropping.

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Still, there may be many positive surprises awaiting oceanographers in the years ahead. It could be that more than 90 per cent of the ocean’s species are still undiscovered. Some scientists estimate that there are anywhere between a few hundred thousand to a few million more to be discovered. Currently, scientists know of around 226,000 ocean species. It is an interesting thought that most sea species are blissfully unaware of the world of humans. Perhaps, for good reason, they prefer to be apart.

When we sail, we go as foreign travellers upon a vast and enigmatic world. For generations, the lure of the sea has fuelled some of our greatest myths and legends, from the birth of Venus to the underwater city of Atlantis.

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Is it any wonder that tales of ghost ships, unmanned vessels plying the waves and then disappearing, seemingly into thin air, should likewise capture our collective imagination? Here are some of the most compelling real-life and legendary tales of ghost ships throughout history. MICHAEL WALSH has written and published many maritime books removed by Amazon on account of the historian’s commitment to the real history of World War II and the Russian Revolution.