Subject: Depth, Pressure, Density of Water

If a one megaton nuclear device was detonated at the bottom of the Mariana 
Trench (Challenger Deep), Would that crack the earths crust?  Also, at that 
depth (7 1/2 Miles) and with the pressure and density of the water, would the 
explosion reach the surface in a dramatic way?

The reason for asking was that I saw a program on the History Channel on the 
Mariana Trench, and they were talking about Density and Pressure of water at 
great depths. I'm just curious. Thank you for allowing me to ask this question.

Re: Depth, Pressure, Density of Water