Shares of cruise company stock Carnival (NYSE: CCL) slipped 1.4% on Wednesday, only to change course and sail ahead 5.4% on Thursday as of 11:35 a.m. ET. The positive note from Stifel Nicolaus, which lies behind today's rally, actually came out on Wednesday. StreetInsider has the details, reporting that investment bank Stifel Nicolaus yesterday reiterated its buy rating, and its $18 price target, on Carnival stock.