An England fan was pulled out of the Ipswich marina by police after he dived into the water to celebrate the Three Lions' victory over Croatia.
Police helped pull the man, wearing only his underwear, out of the water after he dived backwards into the dock on Sunday.
He was surrounded by a crowd of fellow England fans singing the 1996 hit "Three Lions" in the background after Gareth Southgate's men beat Croatia 1-0 at Wembley.
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A spokesman for the Suffolk Fire and Rescue Service said jumping into the water can be "extremely dangerous".
The spokesman said: “Even the strongest swimmers can get into serious difficulties in open water.
"These types of open water can be incredibly deep in places, but very shallow in others - particularly when the water levels drop over the summer. This makes jumping into the water extremely dangerous.
“Even in a heatwave, the water temperature stays very low. It’s so cold it can cause shock or hypothermia.
"Plus the water hides other dangers such as machinery, sudden dips and drops, weeds and mud, and very strong currents created by the changing depths.”
Suffolk police have also called on fans to enjoy the tournament safely and have reminded fans to drink responsibly.
Speaking last week, chief inspector Matt Carney said: "The Euros bring joy and anguish, in equal measures, to fans and we encourage everyone to enjoy the tournament but remember to be considerate, mindful and tolerant of others.
"Alcohol combined with emotion and passion can sometimes lead to incidents of antisocial behaviour and violence, and these have real consequences. There is no excuse for abusive behaviour in any setting, so we urge people to act responsibly.
"If you’re going out to watch the matches, whether that’s in a pub or at any other outdoor screening, remember to look out for your friends and ensure you have arranged how you’re getting home.”
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