Fig.: to utterly impress, surprise, overwhelm, or excite someone in a positive way

Her singing blew me out of the water. I wasn't expecting that and it was beautiful

Il suo modo di cantare mi ha veramente impressionato. Non me l'aspettavo ed è stato bellissimo

I was blown out of the water when I saw the striking resemblance between the girl in that 16th-century portrait at the museum and my daughter

Il vedere l'impressionante somiglianza tra la ragazza di quel ritratto cinquecentesco al museo e mia figlia, mi ha lasciato di stucco

It alludes to the explosion of a ship hit by enemy fire and literally blowing out of the water