Crystal Palace is a boat-access limestone reef off Rottnest Island known for maze-like caves, arches, and swim-throughs cut into the reef. Sunlight filters through the openings, and the site rewards divers who like complex topography, a torch, and controlled buoyancy around overhead sections. The reef is usually dived in calmer weather windows than more exposed parts of the island, but conditions still depend on swell, tide, and daily weather. Expect busy fish life through the holes and along the outer reef, with regular reports of blue groper, Samson fish, buffalo bream, snapper, boxfish, and rock lobster around the ledges and cracks.