Likely not on a yot, mate. After
training, most hires would primarily
work at Buckingham Palace, with about three months per year at other royal residences.
The yacht Brittania is, of course, now a museum, along with the former
racing sailboat Bloodhound. Labour scuttled replacement, and according to Wiki "Proposals for the construction of a new royal yacht, perhaps financed through a loan or by the Sovereign's own funds, have since made little headway." Thus has ended a centuries-old tradition.
It has been mentioned that HM Queen Elizabeth II in 2006 and again in 2010 briefly chartered (one and two weeks) the MV Hebridean Princess, a small luxury
cruise ship (2112 gross tonnage, 72 m length).