1325 ET - Many cruise lines have been offering covert fares--or fares that can only be offered by phone when someone calls to book, and cannot be offered on a website--to select sellers, UBS analysts say, citing a recent conversation with a large cruise seller. The covert fares are largely being offered for last-minute European bookings, as well as upcoming trips to the Caribbean and Bahamas, the analysts say in a research note. "Covert fares are typically a sign that cruise lines don't want to disrupt bookings that are already in hand by having lower rates available in the market," the analysts say. "And interestingly, these covert fares were only being offered to the largest 5-6 sellers, not to most sellers."