You got caught in the rain with no umbrella on your way to work, so you're totally wet. A coworker sees you and says:
You're soaking wet!
"Soaking wet" is a common phrase that means that someone is very wet, usually because of rain. To "soak" means to become filled with water, so this phrase is an exaggeration that compares the wet person to a sponge or something that's completely full of water.
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