Jersey Coastguard is urging boat-users to wear a lifejacket after saving someone who fell into the water at South Pier without one.
The person was trying to get between a dinghy and a boat when they got into trouble and ended up in the sea.
Luckily, they were not in the water long and did not come to any harm, but it did raise concern.
Wearing a lifejacket in cold water can increase a person's chances of survival by up to four times.
Coastguard Manager, Phil le Neveu says the biggest risk is people missing their footing, and it is important to always wear a lifejacket, even when transferring to and from boats and dinghies.
"We have seen several people falling into the harbour during similar transfers and it is especially important to stay safe with the water temperatures we have at this time of year.
"People can quickly suffer the effects of cold-water shock when they are not used to being immersed in the sea during the winter."
If someone is caught in cold water (below 15°C) the advice is to take a minute to let the initial shock pass, relax and 'float to live' and to keep calm and call for help or swim to safety if able.
Cold water shock can affect someone's breathing and movement, so adopting the HELP 'heat loss reducing' position can also aid survival.
Islanders must also check their lifejackets are working correctly.
A properly-maintained one will be able to flip the user onto their back if they roll onto their front in the water.
An automatic lifejacket should also have its components regularly replaced and should have an expiry date and manufacturer stamp.
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