Tales are told of ships that wander into seas where Dragalge live, never to return.
– Pokémon Y Pokédex
Dragalge is the only Poison/Dragon Pokemon; it evolved from Poison/Water to Poison/Dragon. I had one in my X game, used it as my Surfer. The fact that it’s Dragon type is probably because in Japanese lore, sea horses are baby dragons.
It has great Sp Def and Sp Att, but is really slow.