First you have to travel to dewford town using surf, fly, or mr. Brany the guy with the sailboat. When you get to dewford town go to the fisherman that is walking around in town and he will give it to you.
route 119 in the water you can find it with a good rod or a super rod or surfing.
You get the good rod on route 118 where you find Steven, talk to the fisherman.
A fisherman east of mauville city will give you the good rod.
Route 119 (any rod)
Fish with Super Rod on Route 218.
There is no glass rod in Pokémon Emerald, Ruby, and Sapphire. The rods that are only available are Old Rod, Good Rod, and Super Rod.
ever grande city with super rod
Fish with good rod in lilycove city.
A fisherman east on the bank opposite of Mauville
RelicanthNot likely; you have to Dive Underwater to find Relicanth in the seaweed in Ruby.
You can use a good rod or super rod to find carvanha on the route southwest from fortree city.
The super rod is found in Mossdeep City in the house behind the space center.