The complete Pokemon RBY pokedex, part 13

Pokémon Name: Vaporeon
Type: Water
Classification: Bubble Jet Pokemon
Pokédex Number: 134
Ability: Water Absorb
Dream World ability: Hydration
Useful Attacks: Aurora Beam
Location Found:
D/P/P/HG/SS: Evolve Eevee
B/W: Poke Transfer, Dream World (event only)

The water-based form of Eevee also learns moves from the Dark, Ice, Poison and Ground types.

Evolution: From Eevee via Water Stone