The aptly named Ping-pong tree sponge (Chondrocladia lampadiglobus) is a carnivorous sponge. Those ping-pong ball looking things are covered in tiny spicules which the sponge uses to catch tiny crustaceans.
Nudibranch by Dermal Denticles via ferrebeekeeper: Gastropod mollusks - Range: shallow intertidal surf to Most are benthic seafloor dwellers, but some float upside down at ocean's surface or swim in water column.
*SAGAMINOPTERON PSYCHEDELICUM NUDIBRANCH ~ Originally described from Guam, this animal is now known from many parts of the tropical western Pacific Maximal size : 20 mm. Frequently on the reef flat zone and the fore reef zone. (psychedelicum, indeed.