In real life, there would be no explosion to view. I mean, there's no fire and flame or anything.
What do you expect to see?
Sorry, that sounds snarky. There's a good article on the physics of depth charges here:
http://en.wikipedia.org/wiki/Depth_charge
What kills you is the sudden and rapid changes in pressure in the water around you. This is exactly, by the way, why a magnetic torpedo, exploding under a hull, is far more effective than an impact shot.