system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does a natural lake not drain completely into the ground it is above?
gpt
Well, they do, sorta.

It depends a lot on the geology of the area, but lakes that have rocky bottoms will drain less into the ground below them than lakes that have sandy bottoms. Even a sandy-bottom lake though is going to take a bit of time to drain through the sand. You can try this at home (if you have sand, water, and a clear container); basically pile some sand into the container and pack it down (the sand would have been packed down by glaciers and whatever else was there before the lake formed, not to mention that the weight of the water in a particularly deep lake is going to pack it down too [6 ft of water is around an additional atmosphere's worth of pressure]). If you pour the water gently onto the packed sand, you'll notice it doesn't reach the bottom of the glass immediately, but rather slowly seeps into the sand. If this is the case for a couple of inches of sand, you can imagine the effect once you get tens of feet of sand intermixed with solid rock and gravel.

So if lakes are draining into the ground slowly, why do they even exist still? Most natural lakes are fed by streams or rainfall in the area, and most manmade lakes were specifically designed to be fed (usually by a dammed river). The inflow from the rivers and rainfall is usually more or less equal to the water losses from seeping into the ground and evaporating, so lakes stay around the same depth.