Neutrinos are neutral particles, they do not carry an electromagnetic charge. They thus do not cause any Cherenkov light themselves.

What Neutrino detector measure is the Cherenkov light emitted by secondary particles that are created when a Neutrino interacts with the matter inside the detector.

E.g. a muon Neutrino reacts with a water molecule producing a muon, which is a charged particle and thus emits Cherenkov light.

Thanks - but I fell over this sentence:

> but there are other particles that don’t slow down as much and end up moving faster than light.

Not slowing down as much I can understand but shouldn't it read as

"but there are other particles that don’t slow down as much OR EVEN end up moving faster than light."

> In water photons travel at say 200,000km a second.

It really depends on the energy of the photons. There is "dispersion". It's the same effect that causes a prism to split white light into different wavelengths.