1. Obtain the "S.S. Ticket"**: This ticket is given to you by the old man on the lighthouse in New Bark Town after you have collected all 8 badges.
2. Travel to the "S.S. Aqua"**: Use the ticket to board the ship at the docks in Slateport City.
3. Defeat the "Captain": The captain of the S.S. Aqua is waiting for you on the top deck. After defeating him in battle, you will receive the "Whirlpool**" HM.
4. Use "Whirlpool" at the Shrine: Go back to Ilex Forest and use the "Whirlpool" HM on the whirlpool in front of the shrine. This will open the entrance to the shrine.
Inside the shrine, you will find the "Hidden Machine" and the "Rare Candy".
Let me know if you have any other questions about the game!