system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does water seem to get bluer the warmer or colder it gets, like in the Caribbean or the Arctic?
gpt
The really turquoise blue water comes from seeing things under it, such as white sand, ice, etc. 

Very deep water is a very dark blue colour.  And many areas you may be thinking of have very sharp drops into the water and go rapidly to deep water and/or they have dark rock or dark sand for a bottom.

The Caribbean has large shelf’s of very white sand so has large areas of very light water.

But also, opaque water that has a lot of sediment also can be dark as it’s not as transparent.  Equatorial water tends to be very transparent and so bottoms show better, while areas like the Pacific Northwest are full of life and have lots of sediment.