What's a good Pokemon in Black/White to learn Surf and Waterfall but still is useful to the team.(Or Maybe Pokemon Diamond,I have Diamond I could go capture and transfer)
Well, even though it would be harder to find, Sharpedo would be an excellent choice. http://pokemondb.net/pokedex/sharpedo
Others: Kingdra http://pokemondb.net/pokedex/kingdra Dragonite http://pokemondb.net/pokedex/dragonite Gyarados http://pokemondb.net/pokedex/gyarados Mew http://pokemondb.net/pokedex/mew Swampert http://pokemondb.net/pokedex/swampert Whiscash http://pokemondb.net/pokedex/whiscash Latias http://pokemondb.net/pokedex/latias Latios http://pokemondb.net/pokedex/latios Kyogre http://pokemondb.net/pokedex/kyogre Rayquaza http://pokemondb.net/pokedex/rayquaza Arceus http://pokemondb.net/pokedex/arceus Jellicent http://pokemondb.net/pokedex/jellicent
And theres tons of others, but these were just some that I thought they were worth mentioning.
Hoped this helped!
Well if waterfall gyrados is a good pokemon to have since high attack but surf on it isn't really good. For surf i suggest empoleon since high special attack. I don't know if there is any pokemon in black/white or diamond that has the equal amount of stats in both attack or special attack