THE moment Louise Muir's black wetsuit slips into the river there is a gentle ripple and then she is gone from sight.
From the bank looking down, the Clyde gives no clues as to what might be underneath its surface – visibility from up here is zero.
Although Louise, a Police Scotland diver, might be out of sight, she is in constant communication with her colleagues above.
And, watching as a search of the riverbed is carried out, it becomes clear that communication is utterly key.
As she moves in a scalloped shape across a specific search area, the police constable is guided by a rope held by another team member on the bank.
Instructions and information are passed back and forth via radio link.
Should something go wrong, fellow diver PC Jimmy Miller is suited up ready and waiting to assist.
Louise has been a part time police diver for a year but only joined the Dive and Marine Unit West full time three weeks before the Glasgow Times joins the dive unit.
Conversely, Jimmy is one of the most experienced members of the team, having been a diver since 2009 and about to retire.
We've been given exclusive access to police specialist missing person search teams operating in the west of Scotland.
Among these is the dive and marine unit, a highly trained, multi-skilled group who operate across the country on search and recovery missions.
The west unit is 11-strong and lead by a sergeant. The Aberdeen team has five full time and six part time divers so both units will often work together if extra resources are needed.
Jimmy said: "Because it's such a small team we are all aware of what we can do, our weaknesses, our strengths, and it is just a case of..."
Louise takes over: "Having a lot of trust in your colleagues."
Jimmy added: "When we are in the water we know we're going to be as professional as possible and dive to the best of our ability.
"But we also know that should something happen to us in the water that requires assistance, we can trust implicitly every member of the team that they're going to be there."
There have been no serious police diver accidents in Scotland in recent times and Jimmy believes that is because every dive is planned "meticulously" by the dive supervisors.
He added: "Different jobs pose different challenges and that's where years of building up experience helps every dive that we do.
"You could dive the same body of water two days running and it wouldn't be the same dive and that's what is exciting."
While the role is varied, a huge proportion of the work is missing persons searches.
If there is intelligence that a person might be in or near a body of water - whether river or loch or reservoir - then the Dive and Marine Unit is deployed by a police search advisor as part of Police Scotland's wider search response.
They will use a boat or a kayak to get to the likely area and then decide whether to dive or not.
The unit also searches for items dumped during criminal activities, such as murder or assault weapons, and they search boats for drugs and take part in counter terrorism operations.
In a wide variety of interviews with officers from multiple specialisms, The Glasgow Times heard the same sentiment again and again.
No matter what the outcome of a missing person search, police specialists said they felt motivated by a sense of honour to bring that person home to their loved ones.
Jimmy said: "Without a doubt, I have seen some sights.
"People ask why you do this job.
"When you're dealing with things like a missing person, you think of the families involved and what they must be going through.
"The fact that you can bring closure to a family who have maybe lost a loved one who is in the water or suspected to be in the water, the fact that you can help with that process, it does give you a sense of job satisfaction and knowing you are doing a good job."
Louise added: "For me, the way I look at it is that as a team we have a job to do.
"Nine times out of 10 we're looking for somebody where the chances are they are already gone.
"Our job is to get them back to their families and, as Jimmy says, that's the important thing."
While the work is physically and emotionally tough, the divers say they can always rely on one another.
The fact it is a shared experience with other people in the same role and environment helps them carry each other through tough times.
Louise said: "It's hard to explain but when you find somebody, as bizarre as it is, there's not sadness there because you are happy to give that person back to their family.
"There's no way to describe it.
"You're, of course, sad that person's gone but you've known that when you've gone in [the water].
"That's your job to try to bring them back to their family and give them closure.
"There must be nothing worse in the world than always wondering what's happened to a loved one and not being able to give them a proper burial."
While Jimmy and Louise clearly love their work, diving is a specialism suited only to a certain type of person.
Jimmy said: "We dive in situations where there is zero visibility and that is sometimes very, very peaceful.
"It's surreal, you can hear your own breathing and you zone out."
But Louise added: "It's definitely not for everybody.
"Jimmy is saying it's very peaceful but for a lot of people it would be claustrophobic: it's dark, you can't see anything, you're relying on touch."
Louise described the Clyde, where they often work, as "very, very dark".
When they are down under the water, searches are carried out using touch and must be carefully, painstakingly done.
Jimmy said: "The big thing for us is the focus of the search.
"When it's missing persons you're the only person who's been tasked with this job. It's not like you're in there but somebody else is going to come in behind you and do the same job.
"You must focus. Even if you miss by an inch you may as well have missed by a mile and you don't want to be that person who doesn't carry out the job properly."
Searchers will be working against tidal flows or in zero viability at times yet must make sure an entire search area is covered using different techniques and procedures.
Jimmy said: "There's no one person in our team who would say they are experienced and know it all because every single person learns something every single dive.
"You could have 10 good dives and come out of one dive and say, 'That was a nightmare'.
"You've come out of it safely but everything went wrong and you don't feel comfortable.
"Then other times it all clicks into place."
Jimmy had "only ever snorkelled on holiday" before taking up his post but a colleague had mentioned the unit to him and "the idea really started to resonate".
Would-be divers have to pass a swimming test as part of a stringent selection process so he practised relentlessly to ensure he was fit enough.
Police drivers are trained at Scotland's national dive school and often come in with zero experience before being trained to dive up to 50 metres.
They are also boat trained; confined spaces trained; and swift water and flood rescue technicians - a host of disciplines to keep up to standard.
Louise is the only female police diver in the west of Scotland with another in Aberdeen.
She said: "When I joined the police this was what I wanted to do. I wanted to have five years at least on the street and then apply for it.
"I've been part time here for a year and was response at Pollok the rest of the time.
"But I would come down for training and if there were call outs for missing persons at the weekends or at night, I would be part of the team going out and finding that person.
"I love it. I love coming to my work every day. I can't believe I get paid to do this."
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