system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do they measure the depth of caves when there’s no real direct path top to bottom?

I’m talking about the record-holding ones in Georgia (the country) or Mexico. I’ve read a few books about these adventures but never do they go into HOW the depth is accurately measured. I’m 49, but my 13 year old asked me. Let’s pretend she’s 5.
gpt
Pressure, as you go down the amount of air pressure increases and this can be used to find out how low in the ground you are.

It's the same principle which hikers use to measure how high they are while climbing mountains.