Submerged Castle oddities

The Submerged Castle, known internally as yakushima_4, has a number of hardcoded oddities that allow it to work. They are important to remember when editing the Submerged Castle, or making caves that are similar to it, and are documented here.

Blue Pikmin Only

The most commonly known oddity of the Submerged Castle is that non-Blues cannot enter it, even through hacking. One of the entries in the Perplexing Pool's initgen.txt file is commented with for yakushima_4, and the entry itself has code related to Blue Pikmin.

The lock is accomplished by checking Pikmin type and cave ID; these factors can be modified by DOL editing.

Music

In /root/user/Totaka, there is a set of text files that determine the music that plays in each cave. The Submerged Castle is set to play new_01_0.cnd on every sublevel. Normally, this is the theme that plays on sublevel 6 of the Hole of Heroes, but when set to play in this cave, it plays the normal theme. It's unknown how this happens, but it's possible that the Submerged Castle theme is a slowed down version of the aforementioned theme.

The music that plays when facing the Waterwraith is odd, too. If encountered in this cave, its theme(s) will play, but not if it's encountered anywhere else. This probably allows the Bully Den's music selection to work properly.

Waterwraith oddities

Normally, when the Waterwraith spawns via its BlackManTimer reaching 0 for the first time, a cutscene will play acknowledging so. However, the cutscene will only play if the Waterwraith is in the Submerged Castle. In any other location, this will not happen, similarly to the music oddities above. Once again, this probably allows the Bully Den to work properly.

Spawning

In the first four sublevels, the Waterwraith will spawn once the BlackManTimer reaches 0 (set to 300 which is 5 minutes). However, even though the BlackManTimer is present on the final sublevel (it is set to 15 seconds), the Waterwraith will not spawn until the player or a Pikmin reaches the center of the arena (where the egg is located). It is currently unknown how this is achieved and the a attribute setting (which is on 2 for all of Submerged Castle) doesn't seem to be a contributing factor.

Update: the Waterwraith is hardcoded to act differently in the final floor of a dungeon.

Other

Similarly to the Subterranean Complex, the Violet Candypop buds on sublevel 5 will always be there, regardless of how many Purple Pikmin you have in the ship. This is preventing you from not being able to defeat the Waterwraith. Although there are only 2 and they're considerably harder to get to, you can throw the cave's Bulbmin into the flowers, preventing you from sacrificing 80 non-Bulbmin to them instead. It's a great alternative method to raise Purple Numbers so you can lift the Doomsday Apparatus.