The men's Olympic triathlon suffered a rare false start on Monday, leading to some frantic action from associated boats to get the message over to the initially unaware swimmers.
Fifty-six men lined up on a pontoon in Tokyo Bay for the 06.30 local start but as the starter announced "on your marks" around two thirds of them dived in early for the 1,500 metre swim leg.
With those left on the pontoon hoping they had done the right thing, a mini-flotilla of boats and jet skis flew into action to head off the group, with around half of them still ploughing on regardless despite the alert horn sounding repeatedly.
Eventually two jet skis combined to stop the leaders, who returned slowly to the start having undergone a more vigorous 200 metre warm up than they had expected.
The race got underway safely around 10 minutes later.
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