The seafloor stage starts in the sea of the Maricopia Islands. There are many coral with Corsola, Luvdisc, and Finneon. After the coral area, the player enters an area with many seaweed, Lumineon and Cradily. The area then leads down to an underwater cave with Qwilfish and fighting Clawitzer. After leaving the cave, the NEO-ONE then begins to rise up to the surface of the sea. During the trip, there are many Tentacruel. After that, the stage ends near the surface of the water.
A major alternate route can be found in this course. When the Lental Seafloor is at research level 2, the player must throw Illumina orbs on a Clawitzer to cause it to destroy a rock in the seaweed area. The alternate route then leads to another underwater cave with Chinchou. After this, the NEO-ONE begins to sink downwards near various swimming Pokémon such as Finneon and Frillish to the seafloor of the stage. The first part features sand and Clamperl while the second part features Golisopod and many ancient ruins. The stage then ends near some ancient ruins. This alternate route is automatically unlocked at Level 3.
The alternate route must be completed to unlock the course's Illumina Spot.
Alternate routes
- When exiting the cave in the alternate route, the player must throw an Illumina orb at a Lanturn. After a swimming Wailord passes by the NEO-ONE, the Lanturn will be captured by two Frillish, and the player must free it by throwing another Illumina orb at it. The Lanturn will then swim into Lugia's den.
Illumina Spot
The Illumina Spot begins in an underwater area with many rocks. Many Wishiwashi appear in the course, and the player must illuminate them with Illumina orbs to cause them to transform into their School Form. In the first area, they are joined with Finneon, and in the second area, they are joined with Luvdisc. In the last area, they appear on their own, and if they are illuminated, they will eat the NEO-ONE to give it a ride. The course ends on a small rock.