As part of its ongoing efforts to promote every single Pokémon out there, The Pokémon Company has shared special content dedicated to Horsea:
Did you know? Horsea makes its home in oceans with gentle currents. If this Pokémon is under attack, it spits out pitch-black ink and escapes. They swim with dance-like motions and cause whirlpools to form. Horsea compete to see which of them can generate the biggest whirlpool.
Source: The Pokémon Company