To unlock the Third Sea in Blox Fruits, ensure your character reaches level 1500. This is the first step to trigger the notification for the Third Sea quest.
Next, head to the Colosseum and talk to the NPC there. You need to offer an expensive fruit valued at over 1 million Billy. If you don’t have one, you can try rolling fruits at the Blox Fruits dealer every two hours.
After offering the fruit, you must defeat Swan. Once Swan is defeated, return to the Colosseum and speak to the NPC again. This will lead you to the Third Sea boss fight.
Finally, after defeating the Third Sea boss, go to the Green Zone docks and talk to Mr. Captain. He will then guide you to the Third Sea.
By following these steps, you will successfully unlock and access the Third Sea in Blox Fruits. Enjoy your new adventures!