Shares of Royal Caribbean Cruises Ltd. /zigman2/quotes/208854639/composite RCL -2.52% fell 2.4% in premarket trading Friday, after the cruise operator announced a stock deal to buy the remaining one-third stake in Silversea Cruises that it didn't already own from Heritage Cruise Holding Ltd. Royal said paid for the remaining Silversea stake with 5.2 million of its common stock, which represents about 2.5% of Royal's shares outstanding. Based on Thursday's closing price of $47.12, 5.2 million Royal shares would be valued at $245.0 million. That would assume a Silversea valuation of about $735.1 million, a substantial discount to the valuation of about $2 billion when Royal completed the purchase of a two-thirds stake in July 2018. Silversea provides ultra-luxury and expedition cruising. Royal's stock has tumbled 64.7% year to date, while the S&P 500 /zigman2/quotes/210599714/realtime SPX +1.40% has eased 2.4%.