WORLD.WDB is the only .WDB file in LEGO Island, unlike the much more common Interleaf File format. As such, it is generally even less well understood. It does not follow the chunking/streaming conventions of the Interleaf format as it is always read from hard drive.
It is known that WORLD.WDB contains most of the 3D models used by the game and many of the textures (but notably excluding the phonemes, which are in Interleaf files). There have been successful attempts at ripping and even swapping assets from WORLD.WDB, but no known attempts at reconstruction.