We put detectors in flooded mines to detect particles from the sun. The water provided shielding. Shielding from radiation from inside instead of outside?
None of this should be a surprise. The planet Earth is a very complicated vehicle. There is massive solar energy which uses the poles as a carrier, the generation of ozone, the interfield exchange of electrical flux between the ground/sky, upper/lower atmosphere, upper/space zone, then there are the Van Allen Radiation Belts. And those are just some of the 'causes' of the makeup and behavior of Earth within our solar system.
We can be hit by massive bursts of radiation from our own sun or some nearby cosmic event.
Oil is a lubricant produced by barely understood geological forces. What we suck out of the ground is the excess from the process.
Lightning occurs worldwide multiple times per second. Lightning occurs between the earth/sky and the sky/space.
Most of the 'dead' moons of solar system planets may be leftovers from the collision between the planet that became Earth, and a wandering planet from the crossing of our galaxy and another.
We are trying to explain the whole Universe, and we barely understand the Earth.
The water wasn't shielding. It's part of the detector. As the neutrinos interact with water molecules, they release Cherenkov Radiation. The detectors look for the tell-tale flash of blue or UV light.
If this theory was true, there'd be all sorts of detections. I don't believe there are, though.
But think about - and I DON'T hold to many of his theories:
The deepest shaft we go is only a few thousand feet "down: = shielding the detectors from external (cosmic rays) radiation is proved - if only by the increased background radiation the higher you go in the atmosphere. People in the airplanes most of the day get more radiation than people in high altitudes, people in high altitudes get more radiation than people in lower elevations, people in nuclear-power ships on the bridge get more radiation than people shielded below by the steel and reactor shielding, people in engine room of surface ships get more radiation than people in submarines who are behind the same shielding, etc.
The distance from the earth's center to the deepest detector is measured by thousands of miles of shielding rock, not thousands of feet.