[jon_adler]

AFAIK, the Australian system doesn’t operate like this for visa overstays. Your friend may be confused with asylum applications for those who arrive by boat (which isn’t often used in practice).

https://www.unsw.edu.au/content/dam/pdfs/law/kaldor/factshee...

[blindriver]

Yes they arrest them and throw them in jail but not offshore jails. I was wrong about that, I checked with my friend.

[account42]

Detention for overstaying your visa is pretty reasonable. That's not something you do on accident.