Acorn worms were just one of the many types of strange fauna observed while exploring a site dubbed “Twin Peaks" during the 2016 Deepwater Exploration of the Marianas. During the dive, scientists also observed everything from swimming sea cucumbers, carnivorous sponges, and long-legged isopods, to hermit crabs with commensal anemones, pregnant mysid shrimp, many stalked sponges, and several deep-sea lizard fish. Watch a video from the dive.