I've been in a crush at Leeds festival in England a few years ago and it was the scariest thing I've ever encountered.
This wasn't while a band was playing either, it was after all the bands had finished and everyone was trying to leave the arena. For some reason, security hadn't opened all the gates to get out of the exit and everyone - 80-90,000 people were being pushed through a tiny exit that had turnstiles.
It happened really quickly. One minute I'm walking away from the concert, then the crowd gets a bit thicker, then I can't move.
OP is right too, we started moving like a fluid. My feet were firmly stuck on the ground with nowhere to go to, but my body was moving with every wave, pushing me onto the people around me like one of those Weebles toys that never falls down. I kept saying sorry to the girl in front who was crying, but I couldn't move off her.
The worst bit? People at the back were chanting 'Hillsborough! Hillsborough!' which made me realise they didn't care about the crush at all, it was funny to them. I thought I was going to die, honestly, I couldn't breathe.
When I finally got out the crush (someone eventually opened a gate), there were people lying on the floor outside having passed out and other people bleeding. Weirdly, everyone just got on with the festival like nothing happened but it's always stuck with me what could have happened.