The main reason to be in the secret cavern is to fight with the leader of team aqua and suddenly KYOURGA will get away and fight with GROUNDON at sootopolis city.
Kyogre.
wala
Go to Seafloor Cavern and look around.
the undersea one on route 128 i think.
u find it at the seafloor cavern
erwater cavern surrounding sootopolis city
how to get all the tickets in Pokemon emerald?
tm43 in emerald is secret power
SECRET
You can put plants in your secret bases in emerald
The same way you got in, or use the escape rope or the move dig.
Seafloor Cavern. To get there you need surf and dive, and once in there you will need strength and rock smash. Seafloor Cavern can be found underwater in route 128.