1/Supervision
Whether in the sea, river or lake, natural waters harbour more risks and dangers than swimming pools.
It is important to choose lifeguard-monitored bodies of water and to swim within the designated bathing areas. In winter, when supervision is not guaranteed, you should still choose locations frequented by other people or close to a rescue station.
If you have the burning desire to jump in the water in winter and you are not near a populated place or a lifeguard station, try to get someone to accompany you if you can, or at least let one or more of your friends know.
Be aware that rivers are very seldom monitored except near water sports centres. The sudden rise in water level can take you by surprise. Do not hesitate to get someone to accompany you for your open water session.