トモカヅキ Tomokazuki are aquatic yōkai who are found underwater and appear to ama, the deep-diving women who gather oysters, urchins, and other sea creatures. They appear on cloudy days. They are a kind of diving doppelganger; they take on the appearance of the ama who see them. The only way to tell them apart from actual women is the length of the headbands they wear; tomokazuki have much longer headbands. Tomokazuki appear to divers deep underwater. They beckon the divers closer to them, offering shellfish and sea urchins as a way to lure them deeper. They continue to lure the divers deeper and farther away from safety. Eventually the divers are either lured too deep or too far from the shore, and they drown. In order to protect themselves from tomokazuki, superstitious ama will carry magic charms with them while diving; usually in the form of the seiman and dōman symbols on their headbands. One popular explanation among believers is that tomokazuki are the ghosts of drowned ama. Since they are only ever seen by ama deep under the water, belief in tomokazuki is not common. Most of the time, tales of tomokazuki encounters are written off as hallucinations or delirium brought on by the stresses of deep diving—high pressure, lack of oxygen, physical exhaustion, and the fear of being swept away. In one story from Shizuoka, an ama and her husband took a boat out to sea to dive for shellfish. While deep underweater, the ama saw a tomokazuki and quickly surfaced to tell her husband. He mocked her for believing such stupid things, and ordered her to keep working. The ama dove back down as her husband commanded. She was never seen again. In Fukui Prefecture there is yōkai called an umiama, which is very similar to a tomokazuki. When an ama dives down to the sea floor, the umiama surfaces. Then, when the ama surfaces, the umiama dives down to the sea floor. Because of this, it is very difficult to spot this yōkai. However, those unlucky few who do manage to see it become gravely ill shortly afterwards.