A police officer said she believed she would die when a man held her face under water as she responded to an incident.
Pc Angela Melia, 33, panicked and inhaled water and silt when James Brand held her head in the water at a dam in Clackmannanshire.
The incident was recounted at the High Court in Edinburgh where Brand pleaded guilty to assault to injury and the danger of life. Details of the hearing were later confirmed by the Crown Office.
Pc Melia and colleague Pc Mark Ormesher were called to Gartmorn Dam, Sauchie, on the afternoon of July 1. They were responding to a report about two men causing damage to parked cars at the popular spot for walkers and anglers. Brand was one of the men pointed out to officers. The accused, who was standing at the water's edge, appeared to be under the influence of a substance and was swaying from side to side, the court heard.
Advocate depute Iain McSporran said: "He adopted an aggressive and unco-operative demeanour and refused to listen to the officer's attempts to explain why he needed to speak to him. He walked backwards towards the water and was warned against so doing."
The other man said of Brand: "You better watch him, he's a f***ing lunatic."
The officers, who radioed for extra help, seized Brand and tried to pull him away from the water, something the accused reacted "violently" to. He struggled and lashed out with his arms, trying to strike the officers while shouting and swearing at them.
Mr McSporran said said: "All three ended up standing in the water. Then the accused grabbed Pc Melia by her clothing and pulled downwards so that she ended up face down in the water."
Pc Ormesher freed his colleague and used CS gas spray and handcuffs to restrain Brand. Both constables are said to have been "very shaken" by the incident and were checked over at hospital. Pc Melia had muscular injuries to her neck, back and arms. The constable was off work for five weeks and had difficulty sleeping and nightmares, but is said to be anxious to return to full duties as a police officer.
Brand was initially accused of attempted murder but the Crown accepted his plea to the reduced charge. He will be sentenced at a later date.