Blue Button Porpita porpita (aka blue button jellyfish), is not a jellyfish, but a marine organism consisting of a colony of hydroids found in tropical and sub-tropical waters of the Pacific, Atlantic and Indian oceans.
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.
The salp chain - (Pegea confoederata) A salp (plural salps) or salpa (plural salpae or salpas) is a barrel-shaped, planktonic tunicate. It moves by contracting, thus pumping water through its gelatinous body. The salp strains the pumped water through its
Glaucus atlanticus (commonly known as the sea swallow, blue angel, blue glaucus, blue dragon, blue sea slug and blue ocean slug). This little sea slug eats poisonous jellyfish and stores their venom for its personal use