I toured the Warren Lasch Conservatory in North Charleston, SC, back in 2007. I fulfilled a lifetime dream to see the H.L. Hunley. There is a picture of a hole in 1 on the 2 conning towers next to 1 of the glass portholes. There were reports that Federal sailors onboard the Housatonic fired their rifles at the H.L. Hunley when it was spotted near their ship. Confederate general Beauregard had ordered the Hunley's commanding officer not to do a deep submerge during the mission because at least 2 previous crews had drowned during sea trials. Early conservation efforts speculated that the hole in the conning tower was a rifle bullet hole.
bullets will not penatrate more than 14 inches into water.
Even a 50 caliber bullet wont do it.
Here is the mythbuster video to prove it:
https://www.youtube.com/watch?v=yvSTuLIjRm8