Effective.
In the 60's, the Japanese LE used water cannons against the Zengakuran protestors (mainly commies).
Let's just say there were no 'mostly peaceful protestors' setting Tokyo on fire or looting of businesses.
Those protests mostly only lasted a day or so. bwahahaha
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Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good ...