IF YOU’VE EVER REACHED the end of a wonderful cruise and wished it could stretch on forever, then a complete circumnavigation of the globe is your dream ticket. You’ll need considerable resources ($35,000–255,000 per guest, depending on stateroom) and ample time (four months, minimum), but for those who relish cruising, an around-the-world voyage is the ultimate splurge.

Around-the-world cruises usually depart in January, and despite their exhaustive itineraries, they are in exceptionally high demand. Holland America Line’s annual 113-day Grand World Voyage on the ms Amsterdam, for example, which starts its roundtrip from Fort Lauderdale Jan. 4, 2018, sold out more than six months ago.

It’s best, therefore, to plan on a circumnavigation in 2019. The obvious choice is Cunard Line, which originated these long voyages nearly a century ago. Two of Cunard’s modern ocean liners, each carrying slightly more than 2,000 pampered passengers, continue the tradition to this day. The Queen Victoria undertakes a 107-night, Southampton-to-Southampton roundtrip Jan. 10–April 27, 2019, with a westward sailing that incorporates an Atlantic crossing and a Panama Canal transit on its way to ports in Australia, Indonesia, China and Africa. Not to be outdone, Cunard’s Queen Mary 2 strikes a contrary course, sailing eastward on its round-the-world roundtrip from New York City (108 nights, Jan. 3–April 21, 2019) as well as from Southampton, England (94 nights, Jan. 10–April 14, 2019). The voyages will focus on exotic ports of the Far East.

Oceania Cruises offers another 2019 circumnavigation, a Miami-to-Miami roundtrip encompassing 177 days (Jan. 14–July 11, 2019). Oceania’s itinerary is worthy of the nearly six months at sea, with calls in Cuba, Bermuda, Panama, Australia, Polynesia, China, Egypt, Israel, France, Ireland and Canada. Maritime merrymakers can begin this once-in-a-lifetime around-the-world cruise in either New York or Los Angeles on the 684-passenger Insignia.

Complete circumnavigations like those Cunard and Oceania offer are becoming rare, as extended but not fully complete world voyages gain momentum. Silversea Cruises’ all-inclusive world cruise in 2019 (Jan. 6–May 19) takes 132 days to visit 52 ports in 31 countries. It sets off from San Francisco and circles the Earth, going as far as London, although the fare includes business-class air travel to complete the circumnavigation. Well-traveled authors Paul Theroux and Pico Iyer will mesmerize passengers aboard the 388-passenger Silver Whisper on this long voyage. Crystal Cruises and Regent Seven Seas Cruises will launch similarly luxurious world cruises in January 2019, both from Los Angeles, but neither is a complete around-the-world experience. Crystal ventures as far as Monte Carlo in 85 days, and Regent winds up after 131 days in New York City.

Circumnavigations do make for a long vacation at sea, but with a ship and itinerary conforming to your travel dreams, a complete global cruise is the ultimate way to travel the entire world in a single splash.