To get to the Third Sea in Blox Fruits, your character must reach level 1500. Once you achieve this level, you’ll receive a notification to start the Third Sea quest.
Next, visit the Colosseum in the New World, located inside the Kingdom of Rose, Area 1. Here, you need to talk to the NPC named King Red Head, who will instruct you to defeat Boss Don Swan if you haven’t already.
You’ll need an expensive fruit valued at over 1 million beli. You can improve your chances by rolling for fruits every two hours at the Blox Fruits dealer’s cousin. Once you have the fruit, use it to access and defeat Don Swan. If Don Swan is on cooldown, switch to another server.
After defeating Don Swan, head back to the Colosseum and speak to King Red Head again. He will then direct you to defeat the Third Sea boss. Successfully defeating this boss will get you one step closer to your goal.
Finally, go to the Green Zone docks and find Mr. Captain. Talk to him, and he will guide you to the Third Sea. By following these steps, you’ll unlock new adventures and possibilities in Blox Fruits.