Why is water blue?

ANSWER: Because the sky is blue.

This is one of my Chinese-character "theme poems," entitled "Blue Skies, Blue Water" (靑天靑水):

"靑天靑水 (청천청수)"
"Blue (靑) Skies (天), Blue (靑) Water (水)"

天水雨水 (천수우수)
Heaven's (天) water (水) [is] rain (雨) water (水),

雨水川水 (우수천수)
Rain (雨) water (水) [becomes] stream (川) water (水),

川水湖水 (천수호수)
Stream (川) water (水) [becomes] lake (湖) water (水),

湖水地水 (호수지수)
Lake (湖) water (水) [becomes] ground (地) water (水),

地水泉水 (지수천수)
Ground (地) water (수) [becomes] spring (泉) water (水),

泉水白水 (천수백수),
[And] Spring (泉) water (水) [is] white (白) water (水),

白水淸水 (백수청수)
White (白) water (水) [is] clear (淸) water (水),

淸水靑水 (청수청수)
[And] clear (淸) water (水) [is] blue (靑) water (水),

靑水天水 (청수천수)
[So] blue (靑) water (수) [is] sky (天) water (水).