Wendy Trehiou has swum the English Channel six times and Graeme Lowe is the only Islander to have swum an ‘Ice Mile’ in water under 5°C and to have completed the North Channel Swim from Ireland to Scotland.
They both say that this is the wrong time of year to start sea-swimming, despite the increasing uptake.
Their warnings have come after a female swimmer ran into difficulty while swimming in St Brelade’s Bay recently.
An ambulance crew treated her at the scene and she was then taken to hospital.
Ms Trehiou said: ‘Open-water swimming was the fastest-growing outdoor sport pre-Covid-19 and, during 2020, it has grown even more.
‘You can go into the ocean – they can’t take that away. The gyms are closed, the swimming pools are closed but the sea is open. And we had relatively nice weather.
‘It’s well known that sea swimming is very, very good for you. It is known to boost the immune system, improve circulation and reduce stress.’
However, she advised beginners against taking up the pastime in the coldest season and said that even those who had done it before needed to bear new risks in mind.
She said: ‘I would personally recommend not doing it at this point. In March, when people took to the sea, it was still very cold but we had more warmth in the air temperature than we do now.
‘The water temperature at the moment is around 10°C, around a quarter of the body’s operating temperature of 37°C. Over the next two months, it is going to drop further to maybe around seven degrees.
‘People who started sea swimming in the summer won’t have acclimatised to the sea temperatures now. It can be too much of a shock to the body.’
Mr Lowe agreed that, if done safely, open-water swimming could bring great benefits. He said: ‘I have been swimming through the winter in Jersey for over ten years. I do it because I enjoy it and it’s great to see so many other people enjoying it as well.
‘But I wouldn’t at this time. If you have been sea swimming since the summer, as the water progressively got a degree or two colder, you will have got used to it gradually. If you go straight in now, it will be a shock to the system.
‘Just because you see other people do it, don’t assume you can do it yourself. They may have a lot more experience.’
He advises: ‘If something goes wrong in the water, you will not have long to get out so stay close to the shore and get out at the first sign of trouble.
‘You will have plenty more opportunities to swim so always think safety first.’
Ms Trehiou added that sea swimmers should never swim alone and said that they should walk into the water rather than diving or jumping in. She also advised wearing a waterproof watch so they knew how long they had been swimming.
And she said a serious danger came in the half an hour after the swim, in what is called ‘after-drop’, and that it was therefore important to dress in warm clothes immediately after leaving the water.
‘You won’t be aware how cold your body will be post-swim while you are in the water.
‘Your core temperature will continue to drop for around 30 minutes afterwards and this will most likely be when hypothermia will kick in,’ she warned.
