Here's how you can get a Pokemon that knows Waterfalls in Pokemon Crystal:
* Train a Squirtle line Pokemon: Squirtle, Wartortle, and Blastoise can learn Waterfalls by leveling up. This is the easiest way to get a Pokemon that knows the move.
* Find a Pokemon in the wild that already knows it: While less common, some Pokemon in the wild (like Gyarados) can learn Waterfalls naturally.
* Use a TM: Waterfalls is a TM move. You can find the TM at certain locations throughout the game.
Where to find the Waterfalls TM in Pokemon Crystal:
* Goldenrod Department Store: You can buy it at the second floor of the store for 50,000 Pokédollars.
* Blackthorn City: You can find the Waterfalls TM in the shop in the back of the city.
Remember, Waterfalls is a powerful Water-type move that is very useful in battles. Make sure to use it wisely!