Seals are used in many different ways.
In the ocean, they are used to keep fish safe from predators and to seal off islands from ocean-going ships.
In Florida, they also are used for bait, especially in the aquarium.
In Hawaii, seal-related problems have been reported.
The seals that are used by the U.S. military are equipped with GPS technology to track their movements and to monitor their health, according to the Department of Defense.
The military also uses them to check the health of personnel on ships, according the department.