Are sea turtles similar to land turtles?
Sea turtles are characterized by having hard shells, salt-excretion glands, non-retractile limbs, and extensively roofed skulls. Sea turtles cannot retract their head or flippers into their shells the way tortoises can, and need the hard shells and heavy-boned skull to protect them from predators. Also, because they live at sea all the time and drink seawater, they need glands to get rid of the extra salt.
