Hook, line and sinker
Definition 1 of 1
Pro Tip 1/3Metaphoric Meaning
The phrase originally refers to fishing equipment, but is used metaphorically to mean complete belief or acceptance. 
When the magician performed, the audience bought the illusion hook, line and sinker.
Pro Tip 2/3Complete Trust
Used to express that someone has believed something with no doubt or suspicion. 
The con artist's story was so convincing that the victim trusted him hook, line and sinker.
Pro Tip 3/3Emphasizing Gullibility
Using this phrase can suggest someone was naive or easily fooled. 
He told them he was a prince, and they believed him hook, line and sinker.