Caves, especially sink holes and cenotes in mexico actually tend to have pretty clear water. The murkyness in water comes either from organic matter or silt. If there’s no light there is no algae to limit visibility. If the cave has flow the silt is often carried away quickly. If there is no flow the silt will sink to the bottom, clearing up the visibility. Once the silt is disturbed (e.g. by a diver kicking their fin in the wrong direction) it can take a long time to settle again.
Caves, especially sink holes and cenotes in mexico actually tend to have pretty clear water. The murkyness in water comes either from organic matter or silt. If there’s no light there is no algae to limit visibility. If the cave has flow the silt is often carried away quickly. If there is no flow the silt will sink to the bottom, clearing up the visibility. Once the silt is disturbed (e.g. by a diver kicking their fin in the wrong direction) it can take a long time to settle again.