Rather than catching a Wailmer at Lv. 40, you can find one by Surfing on Route 129 or Fishing on Route 136 with the Super Rod. (though they're very rare, I'd say evolve Wailmer)
You can catch a wailord at route 129 by super rod. Their level could be very high, although i met a lvl 28 wailord there by accident.
You Can't
In emerald, there is a slim chance you'll catch one in Route 129, but the easier way is to catch a Wailmer and evlove it.
You cannot catch Wailord. You can, however, catch Wailmer, which evolve into Wailord starting at level 40.
Evolve a Wailmer (Level 40)
Swampert or Wailord.
You do not need a Wailord to catch a Registeel in Pokemon Emerald. You may need a Wailord or any other water-type Pokemon to surf to the place where you catch Registeel, but other than that, you don't need a Wailord.
No, but a 45 wailmer is basically a wailord.
You Can't
no you do not just the Pokemon relicanth and wailord.
I don't think so, but you can catch wailmer near Pacifidlog.
go to route 129 and surf around, there is a 1% chance that one will apear
You can catch Wailord while surfing through Route 129 however it's a rare Pokemon additionally you can find Wailmer in locations such as Mossdeep City, Ever Grande City, Dewford Town and Lilycove City and then you can evolve it at Level 40 which will cause it to evolve into Wailord.
you can find it at rout 129
in shinetown city
wailord you have to evole from wailmer and relican you find in dive mode.
In emerald, there is a slim chance you'll catch one in Route 129, but the easier way is to catch a Wailmer and evlove it.
You cannot catch a Wailord but you can, however, evolve a Walmer at level 45.