"Silvery raindrops were running down his golden breast plate…"
A metal with all the properties of ordinary gold, water silver is quickly recognized if the ore mined is washed with water. Whenever its surface is covered with water, it attains the color and all the properties of silver. An item of this metal fully submerged in water is basically a silver item, while a partially covered one is literally made from gold and silver. This metal even changes it’s weight in water to match that of silver.
Any creature vulnerable to silver is vulnerable to the wet metal. It can be used in alchemy and any reaction as silver, if there is water to mask its surface.
Water silver can sometimes be found in gold veins, forming small streaks in the main vein. If it goes unnoticed to the smelters along with the ordinary gold it alloys perfectly with it, permanently lowering it’s yellow sheen and color to a more dulled shade of yellow (depending on the amount of water silver in the mixture). It generally makes people think that this particular batch of gold had lower quality or some other metal alloyed with it (which is true), and is dismissed.
When mining for this particular metal the ore is broken into smaller bits and then sought through under water for the bits containing the magical metal.