Hi Phil, I used to leave my boat in the water all year round in Holyhead, and would monitor the sea water temperature from the input transducer for my Raymarine log speed. I don’t recall it getting much lower than 4 or 5 degrees Celsius, so on the basis that the sea water temperature would most likely warm the air around the boat I didn’t worry too much about freezing. In more recent years and before selling the boat in September this year I have had the boat lifted ashore in Beaumaris over winter. Having the boat ashore over winter did concern me a little such that I fitted two mains powered pole heaters, one next to the aft fresh water tank and pump, and one next to the calorifier, but the weather didnt get cold enough to use them more than once in the four or five winters it was there. I did remove the shower head, and never put it back in place, mainly because the water around the UK is too cold for me, and I cant swim anyway, so I had no need for an external shower.