off (one/he/she/it) goes!
off (one/he/she/it) goes! {v. phr.}
Said of a person, a vehicle, or a memorable thing who/which has started leaving or moving, both as a statement of fact (declarative assertion) or as a command (imperative).
When the boat hit the water in the formal launching ceremony, they cried out simultaneously, "Off she goes!"
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Source: A Dictionary of American Idioms