An inspector who was in charge of police at a canal where a teenager died has insisted he was right not to ask the officers to go into the water.
Acting Inspector James Reynolds told St Pancras Coroner's Court: "The Metropolitan Police does not expect people to jump in the water but it does expect them to do a dynamic assessment."
This would take into account various factors such as the conditions of the water including potential obstacles, and the officers' ability to swim - but they must communicate a rescue plan.
He was speaking at the inquest into the death of Jack Susianta, 17, of Hackney, east London, who died in a canal at Walthamstow Marshes in July 2015.
Of the response of the police officers who were at the scene, he said: "I was satisfied they were doing all they could do."
He said the officers "appreciated the urgency" and were communicating in a "calm manner" to Jack, who had suffered a psychotic episode, smashed through a window at his family home and fled in just a T-shirt, boxer shorts and socks.
The teenager's mental state also meant he feared the police were not the real police, the jury has heard.
By the time Mr Reynolds had made the journey by car from Jack's home to the scene, the police helicopter, marine support and ambulance were on the way.
Mr Reynolds said members of the Territorial Support Group, who could help with the search, seemed "distraught" and there were quite a few members of the public watching.
Saying the police are not a rescue service, he added: "Once they (the officers) make a dynamic risk assessment, if they choose to go into the water they will not be in trouble."
Knowing that Jack had previously been sectioned and taken to hospital, Mr Reynolds, who was in charge at the scene, had declared him a high-risk missing person.
This meant there were substantial grounds to fear he could come to harm.
Mr Reynolds declared it a critical incident after no-one in a nearby park had spotted Jack. Then he heard that the teenager was in the water.
Officers were throwing 82ft (25m) life ropes to Jack as he became submerged but the teenager did not grab them.
One of the bright orange life ropes, similar to that used, was unfurled inside the court so the jurors could see it.
The rope crossed the diagonal of the court room 3.5 times.
Coroner Mary Hassell said she was posing some of her questions in case lessons could be learned to manage future incidents.
She asked Mr Reynolds if he felt he made the right decision in not asking while he was in the car en route to the scene whether anyone was a strong swimmer.
He said: "Yes, the rationale for me is that it felt like there was an effective rescue plan in place and they were carrying out a dynamic risk assessment."
He described the water as "dismal" and "really oily, dark and you could not see below the surface".
Within minutes of arriving at the scene a police officer had asked to go into the water.
Mr Reynolds said that during this "quite frantic" stage he had not stopped anyone from going into the water.
The coroner told Mr Reynolds that members of the public had volunteered to go in.
He said he did not see or hear that, but that he would have given them a "health warning".
He said he would have told them "if they want to go in there they could be a casualty as well and it is very important to know that they did not know what was below the surface".
Regarding the police officer's request to go into the canal, Mr Reynolds said: "I could not give that authorisation - it is for you to make a risk assessment."
The coroner said one interpretation of that comment is that he was not taking responsibility and was stepping back from the situation.
Mr Reynolds replied: "I think I answered that in the best way that I can. I answered in a way that people (police officers) could understand."
Pc Richard Wilson waded into the water but had to go to hospital afterwards because he felt "a bit poorly after ingesting water", the court was told.
Mr Reynolds said the officer seemed to be a little confused at the time and his teeth were chattering.
The inspector spoke to members of the public about what was going on and the fire brigade had also arrived.
Asked if in retrospect he would have done anything different, Mr Reynolds said: "I did have sleepless nights. I brood about it a lot - it is nothing compared to what Jack's mum has suffered though - but looking back at it, no, I believe not."