Its tail fin billows like an elegant ballroom dress, giving it the nickname of the Water Queen.
– Pokemon Red/Blue Pokedex
Goldeen’s species is just the Goldfish Pokemon. The only thing different is that it has a horn. It looks rather feminine due to its frills and “lipstick” (even though it’s 50% male), and its Red/Blue Pokedex entry calls it the “Water Queen”, which is funny, because it evolves into Seaking.
Because of its horn, Goldeen can learn many horn-based attacks. It can also learn Waterfall by level-up, even though it’s an HM move in most gens.
Goldeen can have the Lightningrod ability in Gen V’s Dreamworld. And in Gen V, Lightningrod not only draws electric attacks to the Pokemon, but also grants it immunity as well as raise its Sp Attack. It’s not very useful to raise the Sp Attack of Goldeen, since it’s got a lot more Attack stat than Sp Attack stat (I’ve killed lots of Goldeens when EV training for Attack), but immunity against electric attacks does nullify one of its weaknesses.