Mercury, Quicksilver
noun, の adjective
This is a fun one. Water silver is mercury, which makes a lot of sense. Mercury is liquidy like water, but it is all silver like silver. So silver water isn't some new mineral water you can get for $4 at the store, it's mercury! Or quicksilver, if you prefer.
すいぎん
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
海魚の体が大きいほど体内にたくさん水銀がたまっています。
The larger the oceanic fish, the more mercury in its body.
何で水星も水銀もどっちもマーキュリーなの？
Why are both mercury and the planet Mercury called "mercury"?
水に落ちたその花は、月明かりで少し水銀色に光って見えた。
The flower that fell into the water appeared slightly mercury-colored in the moonlight.