Four giant craters were found by accident in the muddy floor of Lake Neuchâtel.
The biggest crater is 525 feet (160 meters) wide and almost 100 feet (30 m) deep. Their origin is unknown: Erupting groundwater or methane-gas explosions?

The underwater sinkholes are among the largest and deepest pockmarks ever found in Earth’s lakes.
The giant craters are similar in size to seafloor pockmarks created by methane-gas explosions.
But the researchers think that erupting groundwater excavated these crazy craters. According to the lead author, these craters are, in fact, springs.

They look like crop circles! Underwater crop circles!
The 4 large underwater craters were discovered by accident by geologists in the northwestern area of Lake Neuchâtel. The experts were indeed studying the bottom of the lake for evidence of past earthquakes when they stumbled upon large circular holes in the lake sediments!