Four more cruise lines are returning to guest operations in December.

By the end of the year, 68 cruise operators are set to be in service, including major cruise companies, expedition operators and also niche lines.

Here are the brands welcoming guests in December:

Antarctica21
First Cruise: Dec. 6
Ships: Magellan Explorer  
Region: Antarctica, the Polar Circle and South Georgia 

Antarctica21 is resuming its fly and cruise expeditions to Antarctica after a 20-month hiatus. Using the 2019-built Magellan Explorer, the operator is offering a series of cruises to the region starting early in December.

Through March, the 100-guest vessel is sailing 12 expeditions to Antarctica, the Polar Circle and South Georgia.

Swan Hellenic
First Cruise: Dec. 22
Ship: SH Minerva
Regions: Antarctica Peninsula and South Georgia

Another cruise line launching service in Antarctica, Swan Hellenic is planning to start its inaugural program on December 22.

Recently christened, the new S Minerva is set to offer Argentina-based expeditions in the region through February. 

Australis
First Cruise: Dec. 30
Ship: Ventus Australis
Region: Patagonian Fjords and Tierra del Fuego

After a long operational pause, Australis is resuming service in South America on December 30.

The Chilean-based cruise line is reactivating the 210-guest Ventus Australis for a series of five-night tours to the Patagonian Fjords and Tierra del Fuego. Sailing from Punta Arenas (Chile), the vessel is set to remain in service in the region until early March.

Poseidon Expeditions
First Cruise: Dec. 20
Ship: Sea Spirit
Region: Antarctica and South Georgia

Poseidon Expeditions will restart its expedition cruises to Antarctica on December 20. Aboard the 114-guest Sea Spirit, the operator is offering a total of seven voyages to the region, departing from Ushuaia (Argentina).