Orcas are really amazing animals. This video shows them working together to hunt a crab eater seal. It is hypothesized that they do this to teach younger calves to hunt. They are working together to dislodge a crab-eater seal (which is a pretty cool animal).
Crab-eater seals don't actually eat crabs. They mainly feed on krill. They have these awesome teeth that allow them to filter out the water when they are feeding.