hook, line, and sinker

used for emphasizing how easily a person is fooled or deceived

The idiom "hook, line, and sinker" finds its origin in fishing terminology, representing the complete apparatus used to catch fish. The "hook" is the actual fishing hook, the "line" is the fishing line, and the "sinker" is a weight that ensures the bait sinks to the desired depth. The idiom has been adapted into everyday language to describe someone who has been completely and unquestioningly deceived or fooled.

Despite the dubious offer, he fell for it hook, line, and sinker, investing his savings in a fraudulent scheme.
The politician's charisma and eloquence convinced the audience to support his campaign hook, line, and sinker.
She told a fabricated story, and her friends believed it hook, line, and sinker, not suspecting any deception.
The prank was so well-executed that even the usually skeptical colleague bought it hook, line, and sinker.
The scam artist's smooth talk and false promises had the unsuspecting victims hooked, lined, and sinkered into a financial trap.