You can't. But it really doesen't matter, since there's nothing behind it.
its impossible to get in there unless you have cheats. but there wouldn't be anything in there
Shoal Cave, north Mossdeep City
How do you unlock the door in the old man's house who lives on mossdeep city on Pokemon Ruby
mossdep city really north west corner
You catch staryu in Mossdeep city right behind Stevens house.
you have to
in mossdeep city
in mossdeep city
not
In Pokemon Ruby/Sapphire/Emerald in Mossdeep City.
You have to surf there first. From Lilycove City, you surf to the right till you reach Mossdeep City.
its impossible to get in there unless you have cheats. but there wouldn't be anything in there
Shoal Cave above Mossdeep City
Shoal Cave, north Mossdeep City
How do you unlock the door in the old man's house who lives on mossdeep city on Pokemon Ruby
There's the space center in mossdeep city if that's what you mean.
with your foot