Seadra is a primarily blue seahorse Pokémon. It has no arms or legs. It has a long snout and a number of spikes on its head, on the sides and on the top. Its torso is covered with rough, cream-colored scales. Seadra's pectoral fins have sharp, pointed, cream-colored tips from which it exudes venom. It also has a large tail, which is generally coiled up.
It is capable of swimming backwards while facing forward. Despite being a pure water type, it is capable of learning several dragon moves.
Seadra can swim facing backwards by rapidly flapping its fins and its coiled tail. They will find coral reefs to sleep in. They catch their prey by spinning their body to create large whirlpools which tire their foes. Seadra then swallow the victim whole using their long snout. After the female Seadra gives birth, the male Seadra will take care of the young and its nest. It will viciously attack those who venture too near to its children. Seadra also contains a gene which its pre-evolution did not carry. Whether this gene contributes to its poison or dragon attributes is unclear.