well both of the Pokemon the leaders have, its a double battle, know psychic, and swampert is water/ground so psychic would do some serious damage, i would suggest getting a couple of other Pokemon instead and training them up to around 35s, 40s, or you can get your swampert up to around lvl 50 and then make sure it knows some good moves and then try versing the gym, i would suggest at least 5 or 6 revives and some hyper potions...
good luck!
After you beat the 7th gym leaders talk to steven in mossdeep city.
No, you can't go to the moon to get Jirachi at all in Pokémon Ruby, Sapphire or Emerald, not even after defeating the Mossdeep Gym Leaders.
The hm it self is in Mossdeep, but you have to beat the gym to use it outside of battle.
go into the gym
To get to Mossdeep City, you have to defeat the other six Gym Leaders, and you need Surf. In Mossdeep, there is a Psychic-type Gym, and Team Magma will be in the Rocket place.
There in the gym in mossdeep city by the way the gym leader are actually gym leaders.
You must beat the MossDeep City gym to use the HM for Dive.
Swampert.
It is on Mossdeep City. There are Twin Gym leaders
Go to Mossdeep city and beat the gym.
first you have to get the dive move from steven at his house.then you have to beat the gym leaders in mossdeep city.finnally you dive where the water is black space and then you,ll find yourself underwater.hope you guys can do it.
beat all the gym leaders to get the masterball beat all the gym leaders to get the masterball