The Salton Sea is California's largest body of water, stretching 55 km long and 25 km wide. It's so big, you can't even see the other side, but chances are you've never heard of it. As Derek from Veritasium explains, it was never meant to exist in the first place. And now no one is quite sure what to do with it.

So how do you accidentally create a mini sea? Back in the early 1900s, engineers were trying to figure out a way to irrigate the fields of America's south-west, while also making sure the Colorado River didn't flood. But in 1905, something went wrong, and the Colorado River ended up flooding anyway, and using the new irrigation channels to seep out and flood the entire plain as well. Oops.

The plain, which just so happens to be located very close to the San Andreas Fault, is one of the lowest lying points in North America, at 70 metres below sea level. So it pretty much filled up with the entire volume of the river before the engineers could stop the flooding.

When researchers realised a few decades later that this accidental lake wasn't going to evaporate, they decided to make the most of it, and filled it with fish, built hotels around it, and turned it into the Riviera of California. Derek's even managed to dig up some awesome TV commercials from the '50s and '60s promoting the hotspot.

It seemed like the mistake had paid off, until the fish all started to die off, and algal blooms began to make the sparkly blue water turn a murky brown. Turns out the only inflows come from nutrient-rich agricultural run off, and there's no outflow due to the lake being below sea level, so as water evaporates, more and more salt gets left behind. This means it's become uninhabitable for fish, but aweseome for algae. It also means that technically the "sea" is a lake, because it doesn't open to the ocean.

Right now, there's 50 grams of salt per litre in the Salton Sea, which makes it saltier than seawater, and the whole thing looks (and smells) more like a disaster zone than a former tourist destination. But that doesn't mean it shouldn't be there.

Watch the episode above to hear the strange and sad story of the Salton Sea. As you've probably guessed, there's a bigger message that we can take from this whole mess, and it's to do with the things we choose to focus our attention on. But we'll let Derek tell you about that, because he does it so beautifully. See guys? this is why we can't have nice things.