OP – assuming that you’re near Sheffield given the username, link up with the Sheffield Outdoor Plungers (SOUP) on the socials. They would be the perfect group to spend time with as you’re starting out. Take it slow, bring plenty of layers and hot drinks to warm up with. Don’t worry about not getting all in and staying in for ages at first, cold water even up to your ankles makes a difference!
Oh and please don’t jump in until you’re fully acclimatised. Cold water shock is a thing.
Enjoy!