In a move that will surprise absolutely no one with a healthy fear of dark, watery voids, a Reddit post about a Brazilian lagoon has gone viral, amassing 7,200 upvotes on r/thalassophobia. The post showcases Lagoa Misteriosa ("Mysterious Lagoon") in Jardim, Mato Grosso do Sul, Brazil - a body of water so clear it looks inviting from the surface, but conceals a flooded cave system that divers have explored to a depth of 220 meters (722 feet) without ever touching the bottom.

The lagoon, as it turns out, is a sinkhole formed by the collapse of a cave ceiling, sitting at the bottom of a doline - a depression caused by limestone dissolution. According to the attraction's official website, the cave lies several meters below the surface and was carved out by groundwater movement. Measuring it isn't as simple as dropping a weighted rope into a conventional lake, because the underwater terrain and rock formations make exploration a real pain in the wetsuit.

Adding to the fun: the water is exceptionally clear, with visibility exceeding 40 meters (131 feet), which creates a bizarre visual effect where the blue just keeps going into an enormous underwater void instead of fading to murky darkness. It's like staring into the abyss, but with better lighting.

The deepest recorded exploration was by Brazilian diver Gilberto Menezes de Oliveira in 1998, who reached 220 meters but couldn't figure out the cave's ultimate depth. So technically, the lagoon isn't "bottomless" - it's just that nobody's been arsed to find the bottom yet.

Reddit commenters, naturally, pivoted from geology to the peculiar psychology of cave divers. Some pondered the sort of person who voluntarily enters a dark underwater cave; others noted that specialized cave diving requires extensive training and equipment. One commenter astutely observed that the appeal lies in the danger: darkness, limited visibility, restricted passages, and the distinct possibility of not being rescued easily. Sounds like a vacation.

Meanwhile, skeptics pointed out that technology might actually be able to explore the lagoon, citing remotely operated vehicles tethered for communication. No scientific body has publicly declared the lagoon unexplorable, but no documented full-depth exploration exists either.

The Daily Dot couldn't independently verify all geological and depth claims, relying on the attraction's official website and the Reddit thread. So, for now, the mystery remains - and so does the thalassophobia.