Silversea Cruises sold a two-thirds stake last year to Royal Caribbean Cruises Ltd., which has already ordered two luxury ships and one expedition ship for Silversea. The line currently has five luxury and four expedition ships in its fleet, which sails in more than 800 destinations. It expects to take delivery of the 596-passenger Silver Moon and a Galapagos ship, the 100-passenger Silver Origin, in 2020.