How do you get a s.s aqua in Pokemon liquid crystal?

In Pokémon Liquid Crystal, to obtain the S.S. Aqua, you need to progress through the game until you reach Olivine City. After defeating Jasmine, the Gym Leader, and obtaining the Mineral Badge, head to the dock in Olivine. Speak with the sailor at the dock to board the S.S. Aqua, which will take you to the Kanto region. Make sure to have completed any necessary story events leading up to this point.