Underwater City is a First Sea island hidden beneath the ocean, known for its unique underwater setting and connection to Fishman Lord. Despite being relatively small, it is an important location for players progressing through early-game content.

The island’s entrance is located between Frozen Village and Prison. To access it, players must enter The Whirlpool, a large whirlpool surrounded by three massive rocks in the open ocean. Because the entrance area is fairly small and easy to miss, finding it can be difficult without knowing where to look.

Underwater City can also be approached from Fountain City, but that route is blocked by an invisible wall.

The city is enclosed within a massive protective dome that keeps the surrounding water out. At the center stands a large castle, where the Fishman Lord can be found. The outer edges are surrounded by tall rock formations, while the ground is covered in sand and dotted with large mushroom like trees, giving the area a distinct underwater atmosphere.

Additional Information:

• The Water Kung Fu Teacher is hidden behind the Fishman Commando area near a differently colored wall and teaches Water Kung Fu for $750,000.

• Defeating Fishman Lord gives a small chance to obtain the Trident.

• Blox Fruit do not spawn in Underwater City.