Orca

Orcas turn up throughout the season across Antarctic waters, and the Gerlache Strait is one of the more reliable places to spot a pod cruising slowly along the ice, dorsal fins cutting the surface in single file. They are not whales in the strict sense but the largest member of the oceanic dolphin family, and their diet reflects that opportunism: different populations specialize in fish, sharks, rays, seals, or even other whales, so what you see hunting off the bow can vary a lot from one voyage to the next.

The Antarctic Peninsula and the pack ice further south toward the Weddell Sea are both good ground for encounters, particularly when pods work the floe edges looking for seals hauled out on the ice. Orcas are highly social and travel in stable, matrilineal family groups, so a single sighting is often several animals moving and surfacing in coordination rather than a lone individual.

Despite their fearsome reputation and the name "killer whale," no fatal attack on a person has ever been recorded in the wild, and most encounters from a cruise ship are simply a privilege to watch: a passing pod, a curious spyhop, or the sound of a blow carrying across still water.