Sea Mauville (Japanese: シーキンセツSea Kinsetsu) is a decrepit research facility in the Hoenn region located to the north of Route 108. The second part of the structure can only be accessed by using Dive and contains the Scanner.
Sea Mauville includes both the decrepit platform itself as well as the water area and sandbar outside of the ship; the northern exterior can only be accessed by travelling underwater inside the platform using Dive.
In Omega Ruby, a portal appears at the end of the beam that extends a significant distance east and upwards from the platform if the player has the Clear Bell; interacting with this portal will initiate a battle with Ho-Oh. In Alpha Sapphire, a portal appears at control desk in the submerged control room if the player has the Tidal Bell; interacting with this portal will initiate a battle with Lugia.
In the lower left room of the right side of the hull, when the player enters the room the message "It feels as though you're being watched" will be displayed. If the player examines the left section of the bookcase in the upper-lefthand corner of the room, they will find a blotched out report regarding the history of the facility, after reading which the same message appears. After this, if the player opens a menu such that they cannot see the overworld, upon returning the screen to display the overworld the Odd Keystone appears, enabling the player to battle Spiritomb.
History
Sea Mauville was a facility commissioned by Mauville City and led by Wattson to extract the natural resources of the ocean. Members of the staff included Captain Stern, Lisia's mother, and Professor Cozmo's parents. Due to several incidents, such as the closure of New Mauville, the facility was closed. After its closure, an environmental survey discovered that the ruins had created a unique habitat for Pokémon and plants, such as mangroves, which only grow there and in Mossdeep City. Because of this, its demolition was canceled, and the ruin was revived as a natural preserve.
Items
Due to the rotation of the camera upon stepping on the platform from the southern exterior, the player needs to press left on the D-pad or circle pad to move north, with all other cardinal directions rotated accordingly. While the camera is not oriented this way while the player is in the southern exterior, it is while in the northern exterior.
Apart from the small sandbar which the player can land on after soaring (which contains no items), Sea Mauville cannot be accessed without Surf, so all items located here require Surf to obtain.
Northwest (upper right) item ball in group of three in corner east of (below) TM13 (Ice Beam), accessed via the western (upper) pathway among the boxes
Southwest (upper left) item ball in group of three in corner east of (below) TM13 (Ice Beam), accessed via the western (upper) pathway among the boxes
Southeast (lower left) item ball in group of three in corner east of (below) TM13 (Ice Beam), accessed via the western (upper) pathway among the boxes
Southeast (lower left) of entrance, blocking one of the ways into the western (upper) pathway among the boxes
Northeast (lower right) item ball in group of three in the back of the eastern (lower) pathway among the boxes
Southeast (lower left) item ball in group of three in the back of the eastern (lower) pathway among the boxes
South (lower side) of the entrance, near the water
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
Trainers with a PokéNav by their names will be registered in the Trainer's Eyes or Match Call function after the first battle, and may have a rematch with the player with higher-level Pokémon.
