The term 'WHAT CRYSTAL JELLIES DO WHEN DISTURBED' can be answered with the four-letter word 'GLOW'. Crystal jellies, also known as bioluminescent organisms, are found in the ocean and emit light when disturbed. This light is produced by a chemical reaction within the organism and is known as bioluminescence. When these organisms are disturbed, they GLOW, which is why the answer to this crossword is 'GLOW'.