It would be quite miraculous to bump into Queen Victoria or Mary on a cruise, and I imagine it would just about as unlikely to see Queen Elizabeth.
My wife suggests we may have seen some princesses on our last cruise but none were royals.
All I ask is a tall ship and a star to steer her by; John Masefield
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014, Regal 2014, 2016, Royal 2017
Star Clippers: Royal Clipper 2015