A British woman who went on a two-week dream cruise five years ago is still feeling "seasick".
Michele-Marie Roberts and her husband and two sons went on a cruise to Hawaii in 2008 but the Berkshire 49-year-old says she still feels like she's on board the ship.
"I walked down the gangplank and collapsed - completely blacked out. I got the flight back home and I was staggering all over the shop," Mrs Roberts told the BBC. "I was slurring my speech - on one occasion I blacked out while chopping vegetables.
"It's like the disorientating feeling you get after coming off a waltzer at the fair - all the time. It's horrendous."
When it is at its worst, even lying down doesn't help, she told the BBC in London.
Mrs Robert has been diagnosed with Mal de Débarquement Syndrome (MdDS) - a rare and little condition which translates to literally mean "sickness of disembarkment".
There is no known cure and only there have only been about 100 reported cases.
According to the BBC, MsDS is characterised by constant feelings of rocking, bobbing, swaying and nausea. Other symptoms can include extreme tiredness, cognitive slowing or "brain fog" and mood changes.
When Mrs Roberts sought medical help for her condition she was sent for an MRI scan and tested for multiple sclerosis and a range of other disorders. She was finally diagnosed by doctors at the Royal Berkshire Hospital six months after her cruise.
Mrs Roberts told the BBC that feeling sick and in motion "every minute of her waking life" had ruined her marriage. She said she could no longer look after or home-school her two autistic sons.
"I have days when I feel sorry for myself and there are days when I wake up and I wonder if it's gone away," Mrs Roberts said.
According to the BBC, there are times when the syndrome is particularly debilitating, such as shopping or using a computer.
Strip lighting can also aggravate the feelings of rocking and swaying, she said.
Mrs Roberts said vigorous exercise, swimming and driving helped alleviate symptoms. She does at least two hours of exercise every day to help her cope.
Another British woman, Jane Houghton, has suffered from MdDS since a short cruise 13 years ago off the coast of Spain.
Trying to get a diagnosis took her more than a year. Her GP treated her for motion sickness, sent her for a brain scan then to an ear, nose and throat specialist. She was also treated for depression.
She is now the founder of the UK support group for Mal de Débarquement Syndrome sufferers.
Mrs Houghton, 48, from Cheshire, feels normal only when she is moving, the BBC reports.
"The more motion I am in the better," Mrs Houghton said. explains. "So I love Zumba, but when I stop it looks like I've consumed all the sherry in the trifle."
But she will never go back on a boat, despite loving the sea, because of the risk that her condition could get even worse.