Actually the vagina has no set depth as it it very elastic and can stretch to accommodate a child passing through it. So to answer your question, it would depend on the situation.
"The human vagina depth can vary dramatically, however the average depth is around 6 inches however the largest recorded depth of a vagina was recorded in London, 1916 and the depth recorded was 17.5inches. This is very deep."
Answered Feb 20, 2010
Edited Feb 20, 2010