How do you go through the two guard in aqua hideout

If u are playing sapphire or ruby go to slateport and look for cap'n stern then after team aqua will steal a sub and go back to aqua hideout and u can go in PS u find the master ball in aqua hideout save it for latios or latias in emerald you have to go to mount pyre and beat the aqua leader on mount pyre enter and exit with the other door on the first floor don't go down or up after this do the above