Translations:The Legend of Zelda: The Wind Waker/Unused Textures and Models/180/en

Compared to the final version, it is static and doesn't give off any light of its own (so it looks very dark); thus it was most likely a placeholder. It is visible in the room, but only when not covered by the final version of the lava, some of which was added into the room. The easiest way is to look in the corner near the start, as shown in the screenshot.