How would police arrest someone actually in a swimming pool?

Posted by tissuepapercatmat@reddit | AskUK | View on Reddit | 281 comments

I was at tooting leisure centre yesterday and 7 police cars and three ambulance cars zoomed up...I could see them from the gym. Turns out it was for a heart attack in the pool, but at the time I had no clue and so I started thinking... If someone went loopy with a knife and then just jumped into the middle of the pool, what would the coppers do? If the knife person wasn't an immediate threat to anyone presumably the police couldn't shoot them, but I can't imagine they'd fancy jumping in to have a fight.