How to explode a hard drive

I know this isn't strictly tech, but I felt it's the best place for it.

People talk (on 4chan and such places) of raids by the police on their house to recover hard drives due to suspicions of CP or of pirated content.
I was wondering if anyone knew of a case where someone actually managed to destroy their Hard Drive, either remotley or before anyone could get to it, or any stories of the sort.
Could it hypothetically be fitted with some sort of... remote water filling thing?
Post anything relevant please.

hmm..
Here's a farfetched plan,

Keep another computer running in some secretive area of your house, and network this one with your normal computer, then, just save everything you do to this secret computer. You'll still have a Hard drive hosting the operating system, so it won't look like you're hiding anything.

Like I said, this is somewhat farfetched, but it seems like it would work nicely.