The Seaside Cave (Japanese: 海辺の洞穴Seaside Cave) is a cavern located between Route 21 and Undella Bay. It is accessible as soon as the player gets to Undella Town; however, Black Belt Rocky blocks the player from exploring the cave until they push Team Plasma out of Opelucid City. It is also the first area in the game where an HM is needed to proceed, as Surf is required to reach Seaside Cave via Route 21 or Undella Bay.
Geography
The cavern has two floors and three entrances. One is to Undella Bay, another to Route 21, and another goes to a separate area of Route 21, where the Plasma Frigate is found. The bottom floor has a Strength puzzle.
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.
Special encounters
This section is incomplete. Please feel free to edit this section to add missing information and complete it. Reason: respawn conditions
A Crustle appears here as part of the story. The Colress MCHN must be used in order to battle it.
It has a 25% chance of holding a Hard Stone and a 1% chance of holding a Rare Bone.
