If you work for Maersk you're likely to be on one of the big box boats doing 4-5 month trips between Asia and Europe with a couple of months of leave at the end of it.
BP or Shell means you're probably pootling round the Gulf a fair bit.
If you're on cross channel ferries you do 2 weeks on/2 weeks off so a good job for someone with a family.
Cruise liners run to a timetable so you can pretty much predict what ship you'll be joining and when. They also get 1 on/1 off leave ratios.
All the decent companies pay an annual salary so you get the same pay every month. You can also claim tax back if you do more than 183 days outside the UK.
Everybody gets their own cabin too.
Another difference is that you don't 'deploy'. The only time you get a big chunk of people joining a ship at once is with lascar or Filipino crews (non-officers) where they tend to join/pay off together.
Officers just join a ship to relieve someone who's done their 4 months (or whatever).