Kent Hovind's "theory" states that a giant icy meteor came from the outer solar system, broke up into bits near Earth, the bits became trapped in Earth's magnetic field and fell into the poles, freezing the mammoths where they stood. As the pieces fell they cracked the crust, creating the continental plates and releasing the fountains of the deep, which flooded the planet. The planet also "wobbled," which destroyed the vapor canopy which Kent and others believe existed. The extra pieces of the ice meteor made the craters of the moon and other objects in the solar system, and the rings of Saturn--and I presume the other giant planets, since all of them are now known to have rings.
There are so many problems with this particular bit of insanity that it is actually difficult to know where to begin.
First, the planet's magnetic field doesn't work that way. Period. Full stop. Hovind apparently doesn't understand magnetism OR gravity.
Second, it doesn't matter HOW cold his giant ice meteor was, because given the size he estimates for it, it would have impacted with somewhere in the neighborhood of the amount of force of a thermonuclear device going off every four or so miles across the surface of the planet in an even grid. The mammoths wouldn't have frozen, they'd have been blasted into plasma, and the Earth sterilized.
Third, a shell of water--ice, vapor, liquid, whatever--thick enough to completely block out harmful radiation from the sun and space wouldn't just block harmful radiation, it would block out the light and the heat that makes the planet habitable to begin with. If this shell were somehow resting on the atmosphere itself, it would also exert enough pressure to liquify the gases of the atmosphere. And unless you invoke magic, then no, a spherical shell of water will not remain levitating motionless in space around the planet for any length of time without falling down or breaking up. And even if it somehow *did,* the problems with its opacity still haven't gone away. Earth remains a very cold, very dark place.
And that's off the top of my head. I haven't even talked about the orbital mechanics necessary to sling some of the icy crap to spatter every cratered object in the solar system from a discrete object breaking up on its way to Earth, or how very MUCH mass that would take, or how the pressure needed for "fountains of the deep" would mean the water would be as hot as the rock of the deep earth itself, meaning that Noah and his poor boat would have been cooked and the planet would still boast an atmosphere of live steam today.
Kent Hovind doesn't understand science, but he DOES know how to sell videos and fleece people. But don't take my word for it--here's a discussion of his dissertation. His phD itself is online in various sites, including Wikileaks.