You’ve been saying it in the wrong context forever and now it’s time to stop.
What you think it means: To get an electric shock.
What it actually means: To injure or kill by electric shock.
What you think they mean: The same thing.
What they actually mean: To flounder is to be clumsy and indecisive, flopping around like a fish out of water; to founder is to fill up with water and sink, or figuratively, to fail.