A tide table is right years before it happens
Tides can be computed rather than forecast, so this table was printed before the year began — and the height column visibly narrows, then widens.
Eight days, ruled into rows. Day 01: high water 04:12 at 5.8 metres, low water 10:36 at 1.2 metres. Day 08: high water 11:22 at 5.7 metres, low water 17:53 at 1.3 metres.
One row is ringed in orange, and it isn't the highest tide on the page or the lowest. It's the day the two numbers come closest together.
What is a tide table actually predicting?
The height of the sea at a stated time, printed before the year it describes has started.
That's the strange part. A weather forecast is a guess that degrades the further out you push it — nobody prints next April's rain. A tide table for next April already exists, dated and bound, because the sea's rise and fall isn't weather. It's arithmetic performed on an orbit, and an orbit doesn't need to be observed on the day to be known in advance.
Why can it be computed rather than forecast?
Because the tide is driven by the moon and sun pulling on a fixed, known cycle, not by air that could do anything.
Weather is chaotic — small differences compound until next week is genuinely unknowable in detail. Gravity isn't. The moon's position relative to the earth on the 5th of next August is exactly as predictable as it was on the 5th of last August, so the resulting bulge of water is too. A harbour's own shape adjusts the timing and height locally, which is why every stretch of coast needs its own table, but once that local adjustment is fixed the rest is a repeating calculation, not a bet.
What does the ringed day actually show?
The point in the cycle where the sea barely bothers to move.
Spring tides and neap tides alternate roughly twice a month as the moon and sun line up or work against each other. Read down the height column on this table and the gap between each day's high and low visibly narrows toward the middle of the run, then opens back out — the ringed day sits at the narrowest point, a neap, where the tide comes in and out with the least conviction it manages all fortnight.
The moon, written as a column of numbers
Nobody printing this table mentions the moon once. They don't have to. The narrowing and widening of eight rows of figures is the moon's phase, translated into arithmetic a reader can act on without looking up.
Who actually owns a table like this?
Nobody owns the tide. A specific harbour authority's printed sheet is a different matter.
The heights and times are a physical fact, computed from public astronomical constants and a harbour's surveyed depth — the same way a weather station's plotted symbols are a public notation rather than anybody's invention. What is somebody's property is the actual document a real port authority publishes under its own name: if reproducing a specific real harbour's real table is the point, the permission to use their sheet is part of the job. If it isn't, an invented coastline does the job better, because the numbers can be built to say exactly what your own stretch of water does.
Does this table have anything to do with the ferry that crosses the same water?
Yes — the ferry timetable running the same stretch prints its own caveat underneath the times, and the tide is exactly why it has to.
A crossing scheduled for a falling tide can be running against water a boat would rather not fight, which is part of why that timetable ends with weather permitting rather than a plain guarantee. The tide table doesn't hedge the same way, because it isn't promising a service — it's stating a fact about the water, and the water doesn't need anybody's permission to do what it does.
Does this work for a stretch of coast that isn't in a sailing guide?
Yes — every harbour, causeway and tidal flat has its own version, because local geography changes the numbers even though the moon doesn't.
A rock ledge that only clears at low water, a family causeway that floods twice a day, a beach where the sand disappears entirely at springs — none of those need a boat involved to matter. The table is built the same way regardless of what it's protecting you from getting cut off by.
Isn't a tide table only useful if you're sailing?
No — most of what a tide table decides has nothing to do with a boat.
Anyone whose plans touch the edge of the sea without going on it — walking a causeway, fishing off rocks, digging for bait, timing a crossing on foot — is reading exactly this table, for exactly the same reason a shipping forecast divides open water into boxes for somebody who can't see it: the sea doesn't pause for whoever's asking.
Does it print well?
Yes — a ruled grid in one ink reads cleanly, with the ring as the only second colour on the page.
Keep the grid lines and figures flat and dark against a pale ground; a tide table is dense with numerals and needs the columns to stay aligned rather than decorated. The orange ring is doing all the emotional work here, so it should be the only place that colour appears — everywhere else, one ink carries the whole table.
How do I get one made?
Describe your own coast at JustOG — the days, the heights, and which row gets ringed. Pick a direction, drag the crop frame, see it composited on the real garment, and it's made to order and shipped.
Designs other people have published are in the shop.
Eight rows of numbers, printed before the year began, and every one of them still correct.