Really???? You've been lucky then, that's all I can say! Of my four, there are three who will regularly do that!
My son's boat cat has been with him on the boat since she was a few weeks old. She also goes 'home' in the car with him to Wales, where her sister lives full time apart from occasional visits to the boat. Before they travel he gives them a dose of Zylkene, which is suitable for cats and dogs, and which is supposed to calm them down when facing stressful situations. You can get it from a vet, or buy it on t'internet.