breasts growing off of you

[Ostap]

Did you swim in the pool like all of your teammates did, when they were going through puberty, and they started getting their periods and it's a terrifying event for a young girl to get into a damn pool because you don't know what's going to happen -- you haven't managed things yet? Did you swim with breasts growing off of you and trying to figure out how to move your arms and still win?
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Hello teachers. What does "grow off of you" mean here? Is it about the natural process of breast development in teen girls generally, or is it about something happening specifically in the pool while swimming?

 

[probus]

In AmE some people use "growing off of" instead of "growing on" or "growing out of". It's a synonym for "projecting". Some native speakers, including me, consider it either substandard or a regionalism.

 

[jutfrank]

Is it about the natural process of breast development in teen girls generally?

Yes.