When we were kids we probably didn’t notice an interesting detail from our favorite cartoon. In SpongeBob SquarePants, they had beaches underwater. Now, as adults, we might think this is absurd, but the next fact might surprise you. We don’t really know if the creator of the series knew this, but underwater lakes do exist in real life.

These lakes are called brine pools, and their salinity levels can be very high. Combined with other elements, these concentrations of water are toxic to most animals, including humans. Only certain organisms that are able to withstand extreme conditions can live in or near them.