How do I get past the water in that place where people say you need this badge?

You have to clear the Pokemon Tower, to get the PokeFlute. To be able to do that, you have to get the Scope Silph from the Team Rocket Hideout in the Celadon Game Corner. After getting the PokeFlute, use it next to Snorlax, and catch it, as there are only 2 of them in the game. After that, reach Fuchsia Town, and reach the end of the Safari Zone to get Surf. Then, beat Koga (if you have a Kadabra, he is toast), and you'll be able to use it. You can use it to get Articuno and Zapdos.