What specific phase makes the Leopard Seal's ambush tactic most successful against an adult returning from sea?

Answer

As they surface or attempt to come ashore.

Leopard Seals rely on surprise, waiting near the water's edge or beneath ice to seize penguins as they surface or come ashore after foraging trips.

What specific phase makes the Leopard Seal's ambush tactic most successful against an adult returning from sea?
Predatoranimalwildlifepenguinroyal penguin