"Seadra sleeps after wriggling itself between the branches of coral. Those trying to harvest coral are occasionally stung by this Pokémon's poison barbs if they fail to notice it."
While Horsea may have been a cute little seahorse, Seadra is a full on threat of a water Pokemon. Seadra is known for being incredibly fast, even being able to swim backwards just as fast it can forwards. It was used by Claire in Johto in Ash's final Gym battle, as well as in one of the challenges in the Orange islands.
Seadras Basic Attacks are Water Gun and Bubble, while its Special Attacks are Flash Cannon and Dragon Pulse.