There are few things on earth more mysterious than the oceans - their fathomless depths, still mostly unseen by humans, are one of the last great unknowns of our planet. There's even a name, thalassophobia, for the fear of what could be hiding in the deep. The little we have explored (by some estimates only 5%) contains species stranger than we could ever have imagined.

In centuries past, when even less was understood about our seas, their aura of mystery made them the ideal subject for marine hoaxes. In Europe the most common of these were Jenny Hanivers: modified remains of skates and rays touted as demons, dragons, or basilisks. These animals were chosen for their body shapes and the smiling 'faces' on their undersides - actually their mouths, nostrils, and gill slits, rather than their eyes which are on the top of their bodies.

The Jenny Haniver phenomenon is a possible explanation for the sea monk, which was reported as washing up on the coast of Denmark around 1550. Described by contemporary texts as a cross between a fish and a man in a monk's habit, this miraculous find was interpreted by some as being a merman. Its origins remain unknown, although a 2005 study concluded that it was probably an angel shark (Squatina squatina), as these were once common in the North Sea.

Sharks, skates and rays aren't the only marine animal to have been given the monster treatment, as trade with Asia brought more exotic species to work with. Fake mermaids composed of parts from monkeys and fish, sometimes with additional materials like wood, are recorded in Europe as early as the 16th century. The most well-known of these, the Fiji mermaid, was displayed in London in 1822 and went on to be promoted by the infamous P.T. Barnum.

In the age of special effects, photo editing, and fake news, finds like these are likely to be met with greater scepticism. But our love for a marine mystery is alive and well, and some prefer to stay open-minded. In 2016 a man called Paul Jones shared pictures of what appeared to be mermaid remains on a Norfolk beach - despite Mr Jones' evident love for model-making his post was shared more than 50,000 times, with some commenters arguing that the find was genuine.

Stories of marine hoaxes like these are fun to read about, but we wouldn't recommend trying to make your own. Handling animal remains can be unsanitary, and we think our marine wildlife is fascinating just as it is! So this Halloween, why not learn a little more about the weird and wonderful species in our waters? Who knows what mysteries you'll uncover...

Curious about our underwater world? Check out our marine project Secrets of the Solent.