Officially, I am told that it is actually the Christmas Ship (not Ships), a term which Argosy Cruises has now trademarked. The other ships that follow along in the wake of the "Christmas Ship" (aka The Spirit of Seattle) are officially designated as parade boats, follow boats, or jazz boats. Who knew? The tradition of lighted boats parading on the Lake in December has supposedly been around for 60 years or so (predating Argosy Cruises for sure), so I am sticking with the term Christmas Ships.
At least we haven't gotten so politically correct as to be calling it the Holiday Ship (yet).
[Photo courtesy of the Seattle Municipal Archives]