BASIC RULES RE; PASSPORTS.
Citizens or permanent residents of foreign countries must have passports to enter foreign countries.
Many countries waive this requirement for many citizens or permanent residents entering as visitors.
Most cruise ships hold passports to enable immigration authorities to facilitate the entry of all types of nationalty passengers to enter the country.
Visas are required for those countries who do not have reciprocity, unless passengers disembark with accredited tourist agencies who do not require visas .(The cruise ship, for example)