You can get out of New Mauville without using an Escape Rope.
Use an escape rope,or start a new game;~]
From Mauville City, go south, you'll meet the Fisherman. Surf and keep to east. Then, you reach the New Mauville.
first,talk to the gym leader at mauville(he will be out side the gym)then he will tell you about new mauville,then he will give you the basement key.second,you need to go to the river in front of the trick house and use surf and go forward.you will see a cave.go in and you are new mauville!
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.
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
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!
First beat the Mauville Gym leader, Wattson.
Voltorb is found in new mauville.
You can get a magnemite in New Mauville.
After a certain point in the game, you will see Watson standing in the middle of Mauville outside of his gym. If you talk to him and agree to help him with his problem, he will give you the key to New Mauville.
look for it in new malvile dumb dumb
you get it in the NEW MAUVILLE basement