The Umibozu, or sea monk, is a yokai of Japanese sailor lore: a giant, dark, bald headed figure that rises from the waist up out of calm night water that suddenly turns violent. Some accounts make it roughly human size, others tens of meters tall. It may smash a ship with its hands or ask for a ladle and bail seawater into the boat until it sinks, so sailors handed over a ladle with the bottom knocked out, trusting the yokai’s compulsion to keep scooping while they escaped. Other defenses included blowing tobacco smoke, throwing precious cargo off the bow near Awaji Island, pushing an oar into the creature until it cried out in the Goto Islands, and pouring dissolved miso into the sea in Tohoku. An 1888 Wakayama Prefecture newspaper even reported a hairy, orange eyed creature with a crocodile’s mouth, a lobster’s tail, and a bull’s bellow.

The name ties the monster to drowned priests and the vengeful ghosts called funayurei. A 1687 text tells of a ferry caught in a storm for carrying a lone woman, which calmed only after she threw herself to a black priest crocodile. In 1851 a sailor named Tokuzo broke his town’s ban on sailing at the end of the lunar month, met a 10 foot Umibozu with glowing red eyes that asked if he was frightened, and answered that nothing is as frightening as surviving in the real world. The monster vanished. Meteorologists suggest sailors were seeing towering cumulonimbus clouds or rogue waves, with the eerie calm before a squall supplying the stillness.

• In landlocked Nagano Prefecture, the river version has a head like a giant bronze Buddha statue.
• In Tohoku, Umibozu take the form of beautiful women who challenge fishermen to swimming contests and swallow the losers.
• The 18th century encyclopedia Wakan Sansai Zue links it to a red, human faced soft shelled turtle that weeps and presses its flippers together as if praying.
• Fishermen released such turtles at once and warned them not to take revenge on their fishing grounds.
• In April 1971 a Japanese tuna boat about 40 kilometers off New Zealand reported a wrinkled gray creature it called Kabagon, with eyes about six inches across.