This school of 3-6 inch Sardines is believed to be the largest in the world (seven million!). Like a living silver river, the school ebbs and flows both nearby and off in the distance. Meanwhile, a pair of brown and white Horned Bannerfishes, living in a 4-ft wide barrel sponge below, seem to hardly notice.
The Thresher Shark's unusual 8-10-foot tail is the same length as the rest of its body, and it uses the tail when feeding. When near schools of small fish (e.g., sardines), it brings the tail around and snaps it (like a whip!), creating a sonic wave that stuns nearby fish...which it can then gobble up! The Malapasqua thresher sharks are somewhat unique; they were observed a few years ago whipping the tail over their heads (instead of to the side) to stun their prey.
Nudibranchs (aka sea slugs) come in a dizzying array of brilliant colors, apparently to warn predators that they are poisonous (like Amazon tree frogs). The name "nudibranch" means, literally, "naked lungs" - a reference to the fact that their gills are on the outside of their bodies (the bundle of pink-and-yellow tufts sticking up on the back/left end of its body in this case).
Made famous by the movie, "Finding Nemo", clownfishes (technically this one is a False Clown Anemonefish) and the anemones with which they live have a classic symbiotic relationship. Immune to the anemone's stinging tentacles, which keep would-be predators away, the clownfish brings bits of food (anything it can find) to feed to the anemone. At night, anemones often close up like a basket so that only the underside (reddish in this case) is visible.
My favorite critter - the 6-inch Peacock Mantis Shrimp (which is unrelated to any of the three creatures in its name) sports claws and eyes unequaled in nature. The claws are "cocked" underneath its head (like a praying mantis) and when it releases them, they lash out in the fastest action by any creature on earth. This either impales the prey or creates a shock wave that stuns it. (Mantis shrimp have also earned the nickname "Thumb Crackers" because if you try to touch one, the lashing out claw can literally shatter the bones wherever it contacts your hand.)
The feather-like animals on the reef are Crinoids, which feed by filtering plankton out of the water with their feathery arms (and can crawl around with little claw-like feet). Here you also see a bunch of brown Vase Sponges, and Green Corals (with polyps pulled in, not out feeding).
HARD CORALS of Apo Island make up the next few photos. They're not as colorful as many soft corals, but I've never seen so many healthy hard corals as the acres of them around Apo Island. It was extremely heart-warming and encouraging to see, and fellow divers will appreciate how unusual it is to see this many of them.