[larkeith]

> "Water is blue because it mirrors the sky."

Seeing that people believe this was quite unexpected, at first - it's such an obvious phenomenon looking down into any slightly deep body of water. But on reflection, it makes sense: many (most?) people in the world might live most or all of their lives without going beyond the shorelines of a sea, ocean, or larger lake/river.

It's a good reminder to always be critical of the assumptions you make, and how much they depend on your own context.

(If you ever get the opportunity, visit Crater Lake. The drop from blue to midnight to pitch is beautiful.)

[simonh]

Did you read the whole answer, including the bit at the end?

>...So the major reason the oceans look blue, if they do look blue, is indeed that they mirror the sky.

[StavrosK]

I contest that, the sea looks blue in overcast days too.