I'm sure this has been done but I still had fun. Water world (all terrain settings Off except Lakes set to Extreme) is like Creative Mode for gameplay characters.
I put the graphic of the core relief tile from the ocean cities into my favorite cross-stitch pattern generator, then went to work with a galaxite shovel, maze block, fossil block, crystal block, and normal, crystal, and grimy water (I had to add the grimy water to get a dark background back after accidentally dumping crystal in the outer water XD). I'll cover the interior water patches with glass later, and then decide how to set the chambers up as 'rooms.'