There's little more terrifying than imagining the evils lurking at the bottom of murky, dirty water. Of course, what our minds come up with is usually a lot worse than what's actually there.
Still, imagine the dread conjured up when the three miles or so of the Canal Saint-Martin in Paris - originally built by Napoleon (well, not literally), starting in 1802.
It connects the 68-mile Canal De l'Ourcq to the River Seine and was funded by a levy on wine, trade and fresh water that flowed into the city.
Importantly, the waterway was used to carry building supplies and food to the people of Paris and by all accounts it's just as famous to and revered by locals as the Eiffel Tower is to tourists.
Unsurprisingly, because humans have very little respect for anything, the canal needs to be emptied of waste every 15 or so years, at which point a team of brave people dredge it.
In 2001, authorities retrieved about 40 tons of trash from the water, including a car and washing machines, as well as gold coins and two 75mm shells from World War I.
In January 2016, the operation was carried out once again. It took three months and cost the city more than $10 million, but they were moving around three million cubic feet of water, so that's not actually such a bad deal.
As the water level dropped, fish were rescued and evacuated, and on January 7th the canal was completely empty of water.
And what lay underneath? Well, plenty of rubbish such as glass bottles, shopping bags and traffic cones - we'll blame students for that one - but there were also a whole bunch of Vélib hire bikes, which are Paris' equivalent of Boris bikes.
But that wasn't the weirdest thing that was found. It was the skeletal remains of a mysterious 50 foot sea creature, the likes of which scientists had never seen before.
Only joking. But they did find mopeds, toilets, suitcases and a vintage stereo. And a whole bunch of other rubbish, all of which was laid out for the public to see in plain view, in the hope that people will be more considerate in the future.
"If everyone mucks in and avoids throwing anything into the water," deputy mayor Celia Blauel told the MailOnline, "we might be able to swim in the canal in a few years."
We're not going to hold our breath...
Featured Image Credit: PA