“Hidden beneath the waves, there are creatures beyond our imagination.” David Attenbourgh said in his intro to the BBC documentary series Blue Planet II. And he's right, the ocean's are the least explored areas on Earth, despite making up the vast majority of it. Every year we discover new species from the depths, some of which are so bizarre and alien-like that people can barely believe that they are real.

So far, we know that there are at least 242,000 different species down there because their names are now registered in the World Register of Marine Species. Around 2000 are added to the list each year. But how many more are we missing? Nobody knows, but estimates range from 300,000 to over 10 million! 

As much as there are creatures that have so far managed to avoid contact with us, they can't escape our impact. In the Mariana Trench, the deepest point of the ocean, every single amphipod captured had at least one plastic fiber in its stomach, according to the research published in the journal Royal Society Open Science.

The world produces an estimated 10 tons of plastic a second, and between 5 million and 14 million tons finds its way into the oceans each year. Much of it washes up on beaches, even on the world’s most isolated and faraway islands, such as the otherwise pristine and ecologically important Galapagos Islands.

About 5 trillion pieces currently float on the surface, often in tiny, easy-to-swallow pieces that end up in the stomachs of albatrosses, sea turtles, plankton, fish, and whales. But those pieces also eventually break up further and sink, raining down into the deep sea and onto the unknown creatures that live there. 

The practice of searching the beaches for flotsam and jetsam that washes ashore from the sea is called beachcombing, and has been a popular pastime for many years now. The more serious beachcombers can be found scouring the beaches with metal detectors, hoping to strike it lucky with something interesting that may have found itself washed onto the beach from ancient shipwrecks, or perhaps some remnants of history or wars in the past. However, most of what is found is trash. Still, sounds like a great hobby to have! 

If you do decide to have a try at beachcombing, be aware that local laws about what you can take vary. Most will prohibit you from taking animals and plants away from the shore, although of course a few seashells is going to be just fine. There is also the risk of hazardous materials, like the case of a 41-year-old woman near Hamburg, Germany. She picked up an object from the beach, mistaking it for amber. She then put it in her jacket pocket, laid the jacket down… and her pocket combusted. The object was white phosphorus from a second world war incendiary bomb. 

What happens if a shipwreck happens, and the goods wash up at your local beach? Is it yours to take now? One of the most famous recent examples would be the tale of the MSC Napoli, a cargo ship that was deliberately beached off England's south coast in 2007, to prevent it breaking apart during storms. About 100 containers fell off the ship and washed up on the shore, much to the excitement of local residents.

"Initially intrigued and then delighted, local residents, followed by scavengers from all over the country, descended onto the beach and spent two days and nights frantically looting whatever booty they could get their hands on," ABC reported at the time. "Motorbikes, spare car parts, clothes, make-up, nappies and even Bibles in foreign languages were all rapidly pilfered by grinning beachcombers in a crazed treasure hunt more akin to the days of galleons and pirates." Some years on, and many residents quietly kept all kinds of booty from the containers, including barrels of wine and BMW motorbikes. The incident has gone down as a mad period that villagers will talk about for generations to come.