It depends. Some will actually go after whales, while others prefer seals.
Killer Whales
Killer Whales prey on Grey whales, which are quite big.
Leopard seals, Killer whales, and humans prey upon seals.
Only Killer Whales (Orcas) prey on gray whales.
No animals live in Antarctica: it's too cold to support a food chain on the continent. From Seaworld, "Killer whales are top predators in the sea. Healthy adults have no natural predators, but sharks prey on older, younger, or ill killer whales."
seals or sealions
They are predators.
by hidding in the water
Yes
leopard seals preys on them and their prey is fish.
killer whales are animals.
Killer whales are top predators in the sea. Healthy adults have no natural predators, but sharks prey on older, younger, or ill killer whales.