Pokemon Emerald: Where to Find Sootopolis City (Hidden Entrance)

Sootopolis City is inside a crater on Route 126. You need to use Dive and enter from underwater.

Situation#

You go to the exact location of Sootopolis City on the map.

But when you arrive, there’s only a large rock formation in the middle of the ocean with no visible entrance.

It feels like you’re in the right place, but there’s no way inside.

Standing in front of the rock formation where Sootopolis entrance is hidden in Pokemon Emerald

Surf to Route 126 and stand in the deep water around the large rock formation.
Use Dive.
Swim underwater and find the underwater opening inside the rock formation.
Use Dive again to surface inside and enter Sootopolis City.

You need the Mind Badge from Mossdeep Gym to use Dive outside of battle.

There is no surface entrance. Use Dive at Route 126, then surface inside the crater to reach Sootopolis.