The idiom "all wet" means that someone is completely wrong or mistaken about something. It is used to indicate that someone's idea, opinion, or statement is entirely incorrect or untrue.
For example, if someone says, "I'm sure that it's going to rain tomorrow," and you know that the weather forecast predicts a sunny day, you can say, "Sorry, but you're all wet. The forecast says it's going to be sunny."
The origin of this idiom is unclear, but it may have come from the idea of being soaked through and through, like clothes that are completely wet. In any case, it is a common and informal way to express disagreement or to correct someone's mistaken belief.
In summary, "all wet" is an idiom that means completely wrong or mistaken. It is used to indicate that someone's idea or statement is entirely incorrect or untrue.
• The politician's argument about the tax reform was all wet. (meaning flawed)
• The marketing strategy proposed by the new manager was all wet. (meaning impractical)
• I think your excuse for being late is all wet. (meaning not believable)
• The critic's review of the book was all wet. (meaning completely wrong)
• The scientific theory suggested by the researcher was all wet. (meaning baseless)
• My friend's guess about the movie ending was all wet. (meaning incorrect)