Couple amplifications
Even though Medicare Plans F (grandfathered) and G - Supplemental to Medicare OG, cover up to $50K, that is eventual reimbursement. You’d likely have to front payment, then get reimbursed (like Rx insurance in 80s and 90s)
A vessel may be registered in Holland, but it is likely “flagged” in another country. As a lawyer, this is done so ship operators can take advantage of more corporate friendly laws.
Many non cruise ships are registered in Monrovia, Liberia!