Many of us associate the sea with feeling happy, relaxed and switching off from life's stress.
But there's growing belief that being near, on, in, or under water has a far more powerful impact on our mental, and physical health than we might realise.
The "Blue Mind" ethos, which is the subject of growing European research, is being championed by Californian biologist and researcher Wallace J Nichols, who tells us he believes "the idea that water is medicine will be quite mainstream" within 10 years.
Here we meet some of the people who are already using the power of water to improve their mental health.
'The sea saved me'
"Growing up wasn't very easy," Jessica Cox explains as she looks out across the rugged cliffs of Land's End.
The 32-year-old from west Cornwall has faced dark times, including bereavement, mental health and alcohol issues in her family, and being bullied.
Anxiety and depression have been a challenge throughout her life but things started to spiral out of control when she started secondary school, she explains.
"I slipped into the wrong crowd and got into drinking and drugs from a young age - about 11," Ms Cox says.
The mother of one says her life took a sharp change in direction when she discovered the "escape" of surfing.
"I would absolutely say I was at a turning point where if I had got in one more bit of trouble at school I would have been expelled; if I had got arrested one more time I would have got taken into juvenile prison.
"The sea saved me," she says.
"You can feel tired of life and all the things that are going on, and you get into the water and it literally washes the anxiety away... you feel this release," she says.
"When you're out there you're part of something that's a lot bigger than you, so it humbles you.
"You feel afterwards the feelings of vibrancy and life; it is unexplainable.
"You're just at one with nature, and nature never judges you."
Ms Cox, now a professional surf instructor and mother to a three-year-old girl, says the sea has been her constant through emotional struggles, both pre and post-natal.
"It's a massive thing bringing a baby into the world and I don't think it's given enough respect, to be honest," she says.
"I was definitely very low, I was offered prescription drugs - but didn't take it and I think surfing has been a real antidote."
She has set up a social enterprise called Sirens, which aims to "inspire and empower" women from disadvantaged backgrounds, through surfing.
"Girls are under so much pressure - to look a certain way, be a certain way; then as you get older you need to be a mum but also be successful... you get in the sea and all of that just washes away," she says.
"I have worked with people who have had awful bereavements, suffered from domestic violence, anxiety and depression, are overweight," she explains.
"It can really be life changing."
'It's the only time I've been free since Afghanistan'
"Not much phases you after you've taken a life," says Ben Baker - not his real name.
The British army veteran, who is in his 20s, has struggled with his demons for six years, having tried to take his own life on Christmas Day while on tour in Afghanistan.
He joined the Army in 2011 and was deployed to Helmand Province the following year as a sharpshooter.
"I was involved in multiple contacts with the Taliban... each of my kills was justified, each on video footage, but the toll on me psychologically was massive," he says.
"Whereas colleagues praised me, I was dying inside.
"I don't think there is a soul on this planet programmed to deal with death, let alone killing or watching your mates take that last breath."
Mr Baker says he was discharged from the Army in 2013 and has long battled with terrifying nightmares, being diagnosed with post-traumatic stress disorder (PTSD) in 2017.
"At my worst I was at risk of ending up in serious trouble with the police; my anger was uncontrollable. I hated everything and everyone.
"I don't think I had a day without a flashback, or a full night of sleep in three years," he adds.
It was in May that he decided to start diving as a different way of coping.
"I had tried about nine different psychiatrists, psychologists - I had seen everything. This is the one thing that turned everything around," Mr Baker says.
He learned to scuba dive with Berkshire-based charity Deptherapy, taking a trip to the Egyptian Red Sea.
"This has truly changed my life," he says.
"As soon as you start that descent and the noises disappear, all your thoughts are devoted to the sea and you become weightless.
"I'm sure at every point in someone's life they thought to themselves 'I wish I was a bird', or 'I wonder what it would be like to fly?' Well this is it.
"It is a complete escape from reality."
"Being under water is the only time that my mind has been free from PTSD since returning from Afghanistan.
"I have never done anything that compares to this at all," he says.
"Now when I have night terrors I sit and I watch diving videos. It's something as simple as watching the bubbles."
Mr Baker is emigrating with his fiancee this month so they can be by the sea every day.
'We've moved so far away from nature'
Joseph Sabien, who grew up in a children's home in London, says he "cannot think of one single positive memory" from his youth.
He suffered a "full range of abuse" by "dysfunctional" older children, some of which haunts him to this day.
"Many of the experiences cannot be forgotten. Despite my training and despite having counselling for many years, these experiences and their impact simply run parallel to our lives," says the married father of two.
After suffering PTSD he trained to be a counsellor himself and moved to the south west of England in the 1990s for the "promise of a different life".
A different life he got.
His love for the water grew after he joined a Cornish cliff rescue team and the Falmouth lifeboat crew.
He set up his charity, Sea Sanctuary, 12 years ago due to his "increasing frustration" at the "shortfall of provision" in the community mental health team where he worked.
"As a society we've moved so far away from connecting with nature, to our detriment," Mr Sabien says.
"We're now focused on clever processes like cognitive behavioural therapy and medicine... and we've moved a million miles away from where we started and where we should be."
Sea Sanctuary secured NHS funding to take people with mental health problems on four-day sailing therapy programmes.
It has since helped thousands of people and won awards for its impact.
"There is just something incredibly powerful about the ocean," says the 48-year-old.
"For centuries people have written about the sea in poems and stories and it's at the centre of films, but we still don't quite grasp the magic of it.
"If you can sustain somebody's mental health by introducing them to activities, by being around others, by being on or around the sea, by walking and engaging, sometimes you don't have to get to the other extreme where people are prescribed antidepressants," he says.
"Some people do need medicine, but in fact for a lot of people they don't - they simply don't.
"For me, the sea has been a complete inspiration."
What is Blue Mind?
Although some humans have always instinctively embraced the ideas central to Blue Mind, the movement has in recent years been documented and championed by Californian biologist and researcher Wallace J Nichols who published a book on the subject in 2014.
There are believed to be only a handful of recognised health services embracing the healing power of water in the UK - although Dr Nichols says this actually puts Britain ahead of the US - but the scientist thinks that "in 10 years the idea that water is medicine will be quite mainstream".
"Just as in the early 1990s the notion that eating fresh whole foods, exercising and reducing stress was considered 'Californian' but is now standard advice backed by science," he says.
2018 saw the fifth annual "100 Days of Blue Mind Challenge", as part of which people shared their water-based experiences every day for 100 days on social media.
Lizzi Larbalestier, a UK Blue Mind ambassador, has built her career around the concept that water is medicine, and is passionate about the benefits.
She is a Blue Health practitioner, having run professional coaching for nearly ten years, based in the Cornish seaside resort of Perranporth.
"My clients include many city-based people who are very successful but have lost their connection with nature and they need a bit of heart space and slowing down," she explains.
Ms Larbalestier refers to the "scientific evidence" found by the European Centre for Environment and Human Health research on the benefits of the Blue Mind ethos.
"Clean, healthy water is a fundamental and free health resource to us," she says.
"It is underutilised and undervalued."