Why do some sharks swim constantly?

Answer: To push water over their gills

To push water over their gills ✓ — Correct! Some shark species like great whites must swim to force water over their gills—this is called ram ventilation. Without swimming, they can't breathe! Other sharks can pump water while resting.

To avoid predators — Wrong. Adult sharks have few natural predators. They swim constantly because some species physically cannot breathe without water flowing over their gills.

To maintain body temperature — Wrong. While some sharks are warm-blooded, constant swimming isn't primarily for temperature. It's about breathing for species that lack the ability to pump water over gills.