wow good effort doing 500m!
Yesterday I did the loony dook down my local beach. I haven't been in since October (about 15C) and it was absolutely horrible. I got cold water hyperventilation just from having my thighs in the water. I spent less than 2 minutes total in the water, and got right out and layered up. Today I obviously decided to go for another dip, for cold-water adaptation. A minute legs only then about a minute up to my neck. Didn't bother getting my head wet, my body got the message fine without doing that!
Yesterday we had a serious incident on the beach. An experienced wing surfer snapped his ankle and needed dragged out of the water and up the beach. Luckily for him there were plenty of people about and he got layered up with dry robes and blankets with a pillow for his head. The manager of the local RNLI station was here and he got the local lifeboat to run over and we had two land-based coastguard units attending too. The first paramedic in a car didn't arrive until +1hr and gave entonox and then got a line in and filled matey up with IV ketamine. When the big ambulance arrived, they got his ankle straight and in an inflatable splint, then we finally got him off the beach and transported at +2hr. I've since heard that he's getting a pin put in to stabilise the ankle, and is otherwise OK. That was quite enough excitement for one day I can tell you!
It really made me think how serious just a silly knock can be, when you only have a short window to layer up and get warm before you start suffering severe cold-related symptoms. Another thing I noticed was that someone could very quickly become another casualty if they entered the water to help rescue someone.
There is real safety in numbers! Enjoy your dips and swims with swim buddies and/or land supervision, and stay safe.