Friendly reminder: most of those boats were local fishermen from Britain because Churchill didn't give a shit if his people lived or died. He's also responsible for causing a significant amount of damage in the Blitz becsause he was using ship's cannons to make it look like he was trying to shoot down Germans, and the shells just fell back down on to London.
World War I, and after that first Christmas, high command on both sides made sure to schedule bombardments through the Christmas holiday every year after that.
that was WW1 and as far as i remember Hitler abstained from the Christmas celebration since he realized it would be extremely demoralizing to go back fighting afterwards