# How to manually adjust symbol positioning in \underset?

I have the following:

\underset{{}^u}{\sim}

which looks like the left; I would like it to look more like the right image.

The changes were shrinking the "u", bringing it closer to the tilde, and raising the whole thing so it doesn't hang below the line. I tried using a \raisebox but had no success.

\end{document}