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 Through both of them know if you want to pass the Red Line there are two ways, namely through Marie Joa naval base or through Merman island located 10,000 feet below sea level. They asked for help from Dark King yag Rayleight or once a ship fruit ana Gol D. Roger to make their ship could sink but not damaged. Because the only way towards the other side of the Grand Line pirate is Merman Island.