they are called ; Affinity Cards. You have probably received e-mails telling you how you can earn points towards your vacation on your favourite cruise line. I got one this morning from Norwegian. 
Just for $hitz & Giggles, I decided to look at the rates. 
O. M. G !!!!!!
First of all, the opening rate is determined by your credit worthiness. Anywhere from 12.99%-22.99% !!!!!!!!! If you are late, it can shoot up to ( sit down for this )......29.99% !!
30% interest if you're late. That means, if you buy $100 worth of t-shirts on the ship, it will actually be $130 on your statement !!!!!!!!
People, avoid these offers. Tempting as they are, they aren't worth it. Forget about those bonus points. If you do use a credit card, shop around for a better rate. Like, maybe from the guy in that back alley. He'll only break your arm. Once.
