blow somebody/something out of the water

[hly2004]

Hi
Could you tell me the origin of the idiom?
(I think your answer will help use it more properly)

[Tdol]

I haven't seen an explanation of the origin, though I've looked, but it could come from something like hunting ducks or from naval battles.

[Gafas y Corbatas]

I'm not sure of the orgin, but I can tell you what it means.

To blow something/someone out of the water, means to surprise or shock them in a good way.

Example: That performance blew me out of the water.
Meaning: That performance was much more entertaining than I thought it would be.

(Just a side note, I'd be very careful on how you use the words blow somebody.)

[Homerunner]

This is an expression that, if not derived from Duck Hunters, has at least been sustained by duck hunters. It describes a competitive situation where one side has done so well compared to the other that they are said to have blown the other out of the water. (There is a variant "blew me away" that applies when one person's superlative performance is totally surprising and thus blows one away.)

In duck hunting the competition is between the duck and the hunter. There is an expression that something is so easy that it is like shooting a sitting duck. Usually the duck is sitting on the water and thus the duck gets blown out of the water by the easily aimed blast from the shotgun. The hunter is considered to have an unfair advantage (& in some places unlawful) if the hunter shoots the duck while the duck is sitting (in the water) and thus the sportsmanlike thing to do is to wait until the duck takes wing and attempt one's shot while the duck is flying, thus evening (still not equal) the odds between the duck and the hunter.

When the odds were not even then the lesser opponent is "blown out of the water".

[Asyut]

I would imagine it comes from naval battles, and now usually means to demolish your opponent in an argument or competition.