This form brings together traditions from Shima, Izu, and Echizen in which a diver sees another self in the water. Tomokadzuki duplicates the witness's face, clothing, and equipment. Only the end of its headcloth, hanging much too long behind it, gives the double away. It appears when cloud cover or fading light has dimmed the sea, approaches with an abalone or another shellfish, and then leads the diver toward the darker side of the water. Ama passed down several responses: do not let fear disrupt the sequence of movements, do not reach forward for what the apparition offers, and wear towels or garments bearing protective signs. None was considered infallible. Some stories tell of a netlike shroud falling over the diver. Encounters overwhelmingly occur during solitary work, which is why many communities regarded diving in company as the safest defense. Tomokadzuki can be understood as a revenant that draws people beneath the sea, but explanations based on delirium, fatigue, and hallucination after long periods of diving have also circulated for generations. Whatever its nature, Shima ama marked their clothing and headcloths with the pentagram and lattice known together as Seiman–Dōman. In Antō, the related umi-ama is also said to move contrary to expectation, never allowing the witness a clear view. The legend gives visible form to a diver's most dangerous moment: alone, disoriented, and no longer certain whether the figure in the water is a companion or herself.