Seaking resembles a koi or goldfish, as it is a big orange colored fish with white and black markings. It has a billowing tail fin and similar pectoral fins, all of which are white with black speckles. Along its back, there is another small fin that is pure white. It also has a small to medium sized horn on its head, two big dark eyes, and pink lips with two small, sharp fangs.
Seaking are common in bodies of fresh water. They live in hollowed out boulders in rivers and streams, and are encountered in Kanto, Johto, Hoenn, Sinnoh and Unova. A female has a smaller horn.
In autumn, its body becomes fattier in preparing to propose to a mate. In the spawning season, they gather from all over to travel upriver. During this time, the Seaking males can be seen performing their courtship dances to woo Seaking females. The male also uses its powerful horn to bore holes in riverbed boulders, to keep the Eggs safe, although in other seasons it will make and live in their own nests. Seaking is very protective of its Eggs, defending its Eggs with its life and fighting with its horn. The male and female will take turns patrolling around their nest and Eggs, and the guarding of Eggs by the Seaking goes on for over a month until the Eggs hatch.
Seaking is a very powerful swimmer, as it is able to swim against a river's current, and even waterfalls. It also uses its powerful horn to bore holes in solid rock, so as to keep its Eggs safe.