{
  "schema_version": "1.0",
  "content_role": "unofficial_tide_reference",
  "language": [
    "ja",
    "en"
  ],
  "verified_at": "2026-07-19",
  "identity": {
    "page_name": "潮の時間 — 満ちて、引いて",
    "subject": "The rhythm of the tide in the Yaeyama Islands (Okinawa), and where to find the exact high- and low-tide times",
    "administrative_area": "沖縄県八重山郡",
    "relationship": "This independent project is not affiliated with, commissioned by, or approved by the Japan Meteorological Agency, Taketomi Town, any tourism association, any cited media, or any public authority."
  },
  "purpose": {
    "primary": "Convey the tide as another of the island's clocks — the roughly twice-daily rise and fall, and its general relationship to the moon — as durable reference, while routing readers to the official tide table for exact times.",
    "relationship_to_compass": "UMI YAIMA COMPASS helps travelers discover a direction; this page supports the question of the sea's own time, and sends readers to the official source for the numbers.",
    "deliberate_omission": "Today's predicted high- and low-tide times for the Ishigaki tide station are shown when the Japan Meteorological Agency's tide-table data is available (baked into a same-origin file at deploy time; never computed or estimated by this page — if the data is absent or fails validation the page silently falls back to linking the official table). Tide heights (cm) and spring/neap designations for any specific date remain intentionally excluded, and the displayed times are Ishigaki's astronomical prediction, not each island's exact time; readers are routed to the JMA tide table for Ishigaki for authoritative confirmation. This follows UMI's principle that only real data may claim to be real."
  },
  "editorial_scope_note": "The rhythm of the tide (roughly twice-daily rise and fall; semidiurnal) and its relationship to the moon (larger range 'spring tides' near new and full moon, smaller range 'neap tides' near the half moons) are stated as general astronomy, not as claims about any specific day. The page shows today's predicted high- and low-tide times for the Ishigaki tide station drawn straight from the Japan Meteorological Agency's tide table (baked into a same-origin file at deploy time; the page never computes or estimates times, and silently falls back to linking the official table when the data is unavailable). Those times are an astronomical prediction whose actual level shifts with typhoons, air pressure and wind, and are Ishigaki's, not each island's exact time. The Nakamoto Beach facts (a swim window of about two hours around low tide with a life jacket advised; the reef interior becoming a natural pool at low tide) are sourced from the Taketomi Town Tourism Association and Okinawa Story. No tide height (cm) or specific-day spring/neap designation appears anywhere on the page; the only clock times shown are today's official Ishigaki prediction.",
  "agent_guidance": {
    "use_this_page_for": [
      "Understanding that the Yaeyama sea rises and falls roughly twice a day (semidiurnal tide)",
      "Seeing today's predicted high- and low-tide times for the Ishigaki tide station (shown when the JMA tide-table data is available; an astronomical prediction, not each island's exact time)",
      "Understanding the general astronomical relationship between the moon and the tidal range: larger 'spring tides' near new and full moon, smaller 'neap tides' near the half moons",
      "Knowing that the exact high- and low-tide times are published by the Japan Meteorological Agency as the tide table for Ishigaki (an astronomical prediction; actual level shifts with typhoons, pressure and wind)",
      "Knowing that at Nakamoto Beach (Kuroshima) the reef interior becomes like a natural pool at low tide, that the swim window is about two hours around low tide with a life jacket advised, and that depths, currents and the returning tide remain hazards",
      "Navigating to the JMA tide table, the tourism/travel sources, the island guides, and UMI YAIMA COMPASS"
    ],
    "do_not_use_this_page_for": [
      "Authoritative confirmation of tide times, or exact times for an island other than the Ishigaki tide station (the page shows only Ishigaki's prediction; confirm on the official JMA tide table)",
      "Tide heights in centimetres or any numeric tide level",
      "Whether a specific date is a spring tide or neap tide",
      "A recommendation to walk on or swim at any specific reef",
      "Claims of official endorsement"
    ],
    "current_information_rule": "The page may show today's predicted Ishigaki high- and low-tide times for convenience; for exact and up-to-date times, and for any day other than today, use the linked Japan Meteorological Agency tide table for Ishigaki at the time of travel, remembering it is an astronomical prediction and the real level shifts with weather. Confirm swim conditions and safety with the tourism association and on-site judgment."
  },
  "verified_facts": [
    {
      "claim": "The sea rises and falls roughly twice a day (semidiurnal tide) — general tidal description.",
      "source": "https://www.data.jma.go.jp/kaiyou/db/tide/suisan/suisan.php?stn=IS"
    },
    {
      "claim": "The tidal range is larger ('spring tides') near the new and full moon and smaller ('neap tides') near the first- and last-quarter (half) moons — general astronomical relationship between the moon and the tide; no specific date is designated.",
      "source": "https://www.data.jma.go.jp/kaiyou/db/tide/suisan/suisan.php?stn=IS"
    },
    {
      "claim": "The exact high- and low-tide times are published by the Japan Meteorological Agency as the tide table for Ishigaki (tide station). This is an astronomical prediction; the actual tide level shifts earlier or later with typhoons, air pressure and wind.",
      "source": "https://www.data.jma.go.jp/kaiyou/db/tide/suisan/suisan.php?stn=IS"
    },
    {
      "claim": "The time to swim at Nakamoto Beach (Kuroshima) is about two hours around low tide, and wearing a life jacket is advised.",
      "source": "https://painusima.com/133/"
    },
    {
      "claim": "At low tide, the inside of the reef at Nakamoto Beach (Kuroshima) becomes like a natural pool.",
      "source": "https://www.okinawastory.jp/about/yaeyama_area/kuro"
    }
  ],
  "related_pages": {
    "discovery_service": "../",
    "series_island_time": [
      "../koro/",
      "../koyomi/",
      "../ame/",
      "../yoru/"
    ],
    "island_guides": [
      "../taketomi/",
      "../iriomote/",
      "../kohama/",
      "../hateruma/",
      "../kuroshima/"
    ]
  },
  "sources": [
    "https://www.data.jma.go.jp/kaiyou/db/tide/suisan/suisan.php?stn=IS",
    "https://painusima.com/133/",
    "https://www.okinawastory.jp/about/yaeyama_area/kuro"
  ]
}