Why is keeping animals in captivity good?

When a child looks at an orca, (or a bottlenose dolphin, or any other marine life) at an aquarium, or marine park, they have just gotten a perspective of life in the ocean. For example, they might grow up appreciating marine life, they might clean up beaches, help a stranded dolphin, rescue a seal pup, or even recycling. It will make a huge appreciation with marine life.