Four people have now died at Bawsey Country Park in less than a decade after yesterday's incident in which a man in his 20s lost his life.
Umar Balogun, 16, and Ryan Pettengell, 41, drowned on the same afternoon in July 2013.
20-year-old-man-drowns-at-Bawsey-Pits
Kristers Bednarskis, 22, died after getting into difficulty on August 8 last year.
At an inquest into his death last month, the coroner heard safety officers from West Norfolk council carried out an investigation into the incident.
Community safety manager Andy Nederpel said there was clear evidence site owner Stephen Bacon had carried out improvements and was doing "all he reasonably can".
He added: "The only way to prevent another drowning at Bawsey Country Park is for the public to follow the rules."
More than 40 signs have been erected warning people not to swim in different languages, while a warden also patrols the lakes off the B1145, near King's Lynn.
The inquest heard people would get out of the water when asked by the warden, then get back in after he had moved on. Others would "tell him where to go in no uncertain terms".
Mr Bacon had acted on all recommendations made by the fire brigade in a risk assessment carried out after he bought the lakes.
Senior Coroner Jacqueline Lake coroner recorded a conclusion of misadventure. She added: "People do have to take responsibility for their own safety. If there are warning signs, they are there for a reason and should not be flouted by the public."
The two lakes at the park are flooded former sand quarries. While shallow water around the sandy beach which leads down to the water may look inviting, depths drop away to 20ft or more close to the shore.
Temperatures also plunge sharply in the deeper water, leaving swimmers at risk of cold water shock - even on the hottest of days, such as yesterday.
The RNLI warns: The effect on the body of entering water 15°C and below is often underestimated. This shock can be the precursor to drowning."
Thick weed grows in some areas of the lakes, while there are also believed to be obstructions suck as old machinery abandoned when the workings were flooded decades ago.
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