if you are looking for the new mauville basement then you have to go south of new mauville and find a place to surf in the route between mauville and slateport and you will find it on the right side of the screen
New Mauville MissionMr. Wattson wants you to turn off the big machine at the end of New Mauville by pressing a red button. The cave's full of Electric-type Pokemon and no Trainers.
You can get a magnemite in New Mauville.
You can get it at New Mauville. Also you need to use this HM named Surf.Go through the Cycling Road by using Surf. Then after you get to the Genorator, you turn it off. Then you see a Poke Ball in the East. Then you earned you Thunderstone.
From Mauville City, go south, you'll meet the Fisherman. Surf and keep to east. Then, you reach the New Mauville.
Watson gives it to you
To get to new mauville
It’s in New Mauville, which is a cave on a tiny island southeast of Mauville City. You’ll need HM Surf to get there.
You can find the thunder stone in New Mauville
if you are looking for the new mauville basement then you have to go south of new mauville and find a place to surf in the route between mauville and slateport and you will find it on the right side of the screen
New Mauville MissionMr. Wattson wants you to turn off the big machine at the end of New Mauville by pressing a red button. The cave's full of Electric-type Pokemon and no Trainers.
You can get a magnemite in New Mauville.
In Pokemon Emerald, New Mauville is south of Mauville City. Go to the first Fisherman you see when heading south from Mauville City. Surf on the body of water that he is facing, then turn left. As you keep Surfing east, you will find a cave. If you have a Key from the Gym Leader, Wattson, enter the cave, open the lock, and do your mission for a reward from the Gym Leader!
Wattson, the gym leader of Mauville, should have it. Complete his request for New Mauville and he will give you the TM.
You can get it at New Mauville. Also you need to use this HM named Surf.Go through the Cycling Road by using Surf. Then after you get to the Genorator, you turn it off. Then you see a Poke Ball in the East. Then you earned you Thunderstone.
From Mauville City, go south, you'll meet the Fisherman. Surf and keep to east. Then, you reach the New Mauville.
After you have beaten your dads gym. The leader of Mauville City will ask you to shut down a generator in New Mauville which you will have to surf beneath bicycling road to get to.. There are all kinds of Electric type Pokemon to be found if you stay long enough.