How do you get the boat ticket in Pokemon Emerald?

Defeat the Elite Four and the Champion. You will then return back home in Littleroot where your dad will give you the ticket. Along with beating the Elite Four and the Champion you will go to the Battle Frontier which will have more challenging problems for you to face. You also want to water the strange tree using the wailmer pail to get a Sudowoodo so you can go down the waterfall to Smeargle Cave. You will also be able to catch Rayquaza, Groudon, or Kyogre with the Master Ball you found in the Team Aqua Hideout if you did not waste it on another poke'mon. To be able to have a chance in the Battle Frontier you will have to make sure all poke'mon are at least Level 100 to beat everyone and the Trainer Hill which will be open. If you have any more questions on your Emerald game you can contact me at my e-mail which is EowynCroft11@live.com.