Petalburg City.
In Pokekon Sapphire, you get the 5th badge after defeating your opponent in a Gym Battle at Petalburgh.
The fifth badge is in Sootopolis City, you need Surf, Dive, and Whirlpool to get it
Get the next badge
You have to go to Wally's parent next door and get HM 03(Surf).
to petalburg city
the third badge in sapphire is at mauville city(north of slateport city)
In Pokemon Red, the fifth badge is possessed by the Poison-Type Koga. The badge is named Soul Badge. It lets you use Surf outside of Battle.
It is the balance badge where you fight Norman(your father) in Petalburg City .
Go to lavaridge town for your next badge.
You have to beat flannery
You get the third badge in sapphire when you get to Mauville. You have to battle Gym Leader Wattson in the Mauville City Gym.
you can get the fith badge by going to petalburg the poke gym there.