I have heard there are exemptions so perhaps offshore (and perhaps merchant shipping) is different.
It happens all the time, I’m sure its more common than we realise at my employer too if overtime isn’t input on the correct system.
Sister-in-law is expected to be on call for 48hrs over the weekend and then has a shift scheduled on Monday so often doesn’t get a decent rest period for 2.5 days, but not wanting to rock the boat she has to deal with it. I don’t think many are aware of their rights (or it doesn’t suit them as they like the extra cash!)