How do you get the move Waterfall in Pokemon Diamond and Pearl?

Answer 1

First, go to Sunyshore City. Then, an Elite Four member named Flint will come up to you and tell you about how the Gym Leader hasn't a very good battle in a long time. Flint will tell you to light a fire in his heart. Go to the Lighthouse (located in the Southeast part of Sunyshore City, accessible by the top pathways). You will see a spiky-haired blond guy looking through some binoculars (this is Volkner). Once you talk to him, he will then go back to the Gym (located on the northwest side of Sunyshore City, also on the top pathways). Go to the Gym. It has some challenging trainers who all use Electric-type Pokemon, who are weak to Ground-type moves. It takes a couple of minutes to figure the whole gym out. These trainers are some of the hardest in Sinnoh. Unfortunately, you cannot avoid any of the trainers. Ground-type Pokémon are recommended, but Water- and Flying-types are not. At the end, you will reach Volkner. Save the game and defeat him. It is very hard though because he has Octillery, which is a Water-type Pokémon. Now go to the small beach North of Sunyshore City and there you will find Jasmine, another Gym Leader from the Johto region. After she sees the Beacon Badge that you just received, she will hand you the HM07 containing the move Waterfall. This is the only way to access the Victory Road, along with Surf, and the Pokémon League, along with a number of other HM moves.