This is a composite of the same Moon Jellyfish taken in succession at the Monterey Bay Aquarium. The Moon Jellyfish is sometimes called the Saucer Jelly or the Common Jellyfish. It grows up to 15 inches in diameter. The adults live 3-6 month and are found in temperate and tropical oceans and bays worldwide.
To see this image best, click on it to enlarge it. The photos were taken with a Canon EOS 40D, EF17-40mm f/4L lens, 1/40 sec (handheld) at f/4.0, ISO 800 on SanDisk Extreme IV Digital Film.