Every ring is one day of 2025 at one harbour: the clock runs around the
circle — midnight at the top, noon at the bottom — and the water's height pushes the
line outward. Stack a year and the ocean's signature appears. Bright rings are spring
tides, the fortnightly heave that follows the new and full moon. Tap or hover any ring.
Data & source
Source: NOAA CO-OPS harmonic tide predictions for 2025,
hourly, local standard time, heights above mean lower low water · fetched
— · public domain. These are the astronomical tide — what the
Moon and Sun alone would do. Real water also answers to wind, pressure and storm surge,
so an observed day can sit well above or below its ring. Six harbours chosen for
contrast, not coverage; the character label is the standard form factor
F = (K1+O1)/(M2+S2) from NOAA's own published constituents.