Gee, another idiot who'll yap on cluelessly. READ the linked articles, if you can. The microwave makes people uncomfortable, without damaging them! If you stand there, uncomfortable, for long enough you might explode, I suppose. Most people just find a new place to stand. Used on crowds, the idea is to quell riots. More importantly, the train in the film was MOVING over a fixed water main. That means the rays are always focused on the water in the pipes, not on moving targets (people).
Yes, the sewer pipes burst right away. No way that happens in real life - there's too much water to heat up. Plus there's the matter of penetrating all that concrete and steel. That's all artistic license for the sake of the film, and if one wanted to criticize the weapon in an intelligent and informed way (not that this stops some people), it would be on that basis. No one wants to sit around waiting for water to boil, so they showed the mains popping like teakettles. Aside from that, the film described pretty much the way that sort of weapon works, if the goal is to destroy a water supply.
I learned about this sort of thing while doing PR for an engineering institute that was working with the US military on various projects. But don't let the facts stop you! Do drone on witlessly, we are all so impressed.
