Let $p:M\rightarrow N$ a surjective submersion of manifolds. Let $Y\subset N$ I want to prove that
$Y$ is a submanifold of $N$ if and only if $p^{-1}(Y)$ is a submanifold $M$.
I could prove that if $Y$ is a submanifold then $p^{-1}(Y)$ using the regular point theorem, but I could not prove the converse.
Any hint?