As of late last year, the weakest of the 3 large listed cruisecos appears to be Norwegian, as far as cash flow goes. Strongest is Carnival (highest cash position, and can cut dividends and stock buybacks by $2 bn p.a. if necessary). Royal Caribbean in between but appears to be stronger than Norwegian. As far as operating margins go, reverse is true (NCLH has the highest, CCL the lowest).
My exposure will only be $50 for a CCL line deposit (banking on cruise cancellation before final payment date).