What a tide table is telling you
Explainer · Last reviewed 2026-08-14
A literacy page rather than a mechanism page: what the numbers in a tide table mean, what they are measured from, what they do not tell you, and why the height matters as much as the time.
Safety
Tides and being cut off — Can cause serious injury or death
Reading the time and ignoring the range, or using a table for the wrong place, puts people on ground that floods faster and earlier than expected. On flat ground with a large range the water advances faster than a person can walk, and it frequently arrives from behind through channels rather than from the seaward side.
What reduces it: Use a table for the actual location or apply the published local difference; read the range as well as the times; decide the time you will leave before you start fishing and set an alarm for it; and treat a strong onshore wind and low pressure as reasons the water will be higher and earlier than predicted.
Worse when:
- Spring tides, when the range and therefore the speed of advance are greatest
- Flat sand, mud and causeways where the water spreads rather than rises
- Onshore gales and low barometric pressure, which raise the actual level above prediction
A TIDE TABLE GIVES FOUR THINGS PER DAY ON MOST COASTS: the times of two high waters and two low waters, and a height for each. Almost every practical use of it depends on reading the heights, and almost everybody reads only the times.
WHAT THE HEIGHT IS MEASURED FROM. Predicted heights are given above a datum — a fixed reference level, in most modern tables the lowest astronomical tide, the lowest level predictable under normal conditions. So a height of 0.6 metres does not mean the water is knee-deep; it means the surface is 0.6 metres above that reference. What matters practically is not the absolute figure but the DIFFERENCE between consecutive high and low water, which is the RANGE.
RANGE IS THE NUMBER THAT DECIDES THE FISHING. Range sets how much water has to move, and therefore how fast the tidal stream runs. A four-metre range moves a great deal more water in the same six hours than a two-metre range, and the difference shows up as the strength of the flow, the size of lead needed, how far the water advances over flat ground, and how much of the shore is exposed at low water.
SPRINGS AND NEAPS ARE THE RANGE CYCLING. Around new and full moon, the solar and lunar influences align and ranges are largest: SPRING TIDES, which have nothing to do with the season. Around the quarter moons they oppose and ranges are smallest: NEAP TIDES. The cycle takes roughly a fortnight, and it is why the same mark at the same clock time fishes completely differently from one week to the next.
WHAT THE TABLE DOES NOT TELL YOU, and this is the part that matters for safety.
IT IS A PREDICTION, NOT A MEASUREMENT. Barometric pressure and wind push real water levels above or below prediction, sometimes substantially. A strong onshore wind with low pressure produces a higher and earlier high water than the table says.
IT IS FOR ONE PLACE. Times and heights differ along a coast, sometimes by hours within a single estuary. Using a table for the nearest port without applying the local difference is a common and occasionally serious error.
IT SAYS NOTHING ABOUT WHEN THE STREAM RUNS. High water and slack water are not the same moment. On many coasts, and especially in narrows and estuaries, the tidal stream continues to run for a considerable time after high water. A table tells you about water LEVEL; the stream is a separate thing and is given in tidal stream atlases and local knowledge.
AND IT SAYS NOTHING ABOUT SWELL, which arrives from weather that may be nowhere in sight and is the thing most likely to hurt you.
Working out the height at a time the table does not give you
A table gives four numbers a day. Almost every question an angler actually has is about a time in between them, and there is a rough arithmetic for it that is worth knowing because it is doable in your head on a beach.
THE RULE OF TWELFTHS. Divide the range into twelve parts and the interval between high and low into six hours. The water moves roughly one twelfth of the range in the first hour, two in the second, three in the third, three in the fourth, two in the fifth and one in the sixth. So half the total movement happens in the middle two hours, and almost nothing happens in the first and last.
WORKED, BECAUSE THE RULE IS USELESS UNSTATED. High water 5.4 metres at 09:00, low water 1.8 metres at 15:00. The range is 3.6 metres and one twelfth is 0.3 metres. By 10:00 the water has dropped 0.3 metres to 5.1. By 11:00 another 0.6, to 4.5. By 12:00 another 0.9, to 3.6 — half the range gone in three hours. By 13:00, 2.7. By 14:00, 2.1. By 15:00, 1.8.
WHAT THAT IS FOR. A gully that fishes at four metres of water has a window from before nine until around half eleven, not until three. A causeway that covers at 3.5 metres is safe to be beyond only after about noon on that tide, and the water comes back at the same rate it left. And the fast middle hours are when the stream runs hardest, which is both when the fishing is often best and when a plain lead stops holding.
IT IS AN APPROXIMATION AND IT IS WRONG IN PREDICTABLE PLACES. The twelfths assume a smooth, roughly six-hour, roughly symmetrical tide. In estuaries the flood is often much faster than the ebb; in the Solent the curve is not one hump at all. Where the shape of the tide is unusual, the local tidal curve for the port is the only honest source and the rule of twelfths will mislead you.
Authoritative guidance
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
- NOAA Ocean Service tides and water levels educational tutorial — National Oceanic and Atmospheric Administration, United States (Government fisheries body)Relied on for: Public education on tidal generation, the semi-diurnal cycle, spring and neap tides, datums and how predicted tide heights are produced.States this directlyPassage read and verified
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling practice as reported by practitioners, including shore technique, terminal tackle, bait and species behaviour.States this directlyCitation checked — the work exists and is described correctly
The four things a tide table cannot tell you
A tide table is astronomy. Everything below is weather, geography or your own arithmetic, and each of them routinely makes the real water level differ from the printed one.
ONE — SECONDARY PORTS NEED CORRECTING, AND THE CORRECTION IS BOTH TIME AND HEIGHT. Most tables are computed for a handful of standard ports. Anywhere else is given as a set of differences: so many minutes on the time of high water, so many minutes on low, and a height difference that is often different at springs than at neaps. Using the standard port's numbers at a mark thirty miles away is the commonest tide-table error there is, and the size of it can be over an hour.
TWO — WEATHER MOVES THE WATER. Low barometric pressure raises sea level and high pressure depresses it, on the order of a centimetre per millibar; a strong onshore wind piles water against a coast and holds the ebb back; a strong offshore wind does the reverse. The combined effect on a shallow coast can be well over half a metre and can delay a high water substantially. A surge is precisely the thing a table does not model.
THREE — TIME BASE. Tables are published in a stated time standard, and in Britain that usually means the times are Greenwich Mean Time and you must add an hour in summer. An hour is the difference between a safe walk back and a wet one.
FOUR — THE TABLE SAYS NOTHING AT ALL ABOUT THE STREAM. High water is not slack water on most coasts. The tidal stream can still be running hard at the top of the tide and can turn before or after it, sometimes by more than an hour, and where the stream runs is a matter of local geography. For fishing purposes the stream is what matters more, and the source for it is a tidal stream atlas or local knowledge, not the table.
WHAT THIS PAGE DOES NOT ADDRESS is whether any particular mark is safe on any particular tide. That is a judgement about the ground, the exit, the weather and the person, and FishingHQ does not state what any current rule is or make that call for a reader.
Authoritative guidance
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
- NOAA Ocean Service tides and water levels educational tutorial — National Oceanic and Atmospheric Administration, United States (Government fisheries body)Relied on for: Public education on tidal generation, the semi-diurnal cycle, spring and neap tides, datums and how predicted tide heights are produced.States this directlyPassage read and verified
- Met Office shipping forecast, inshore waters forecast and marine warnings — Met Office, United Kingdom (Government fisheries body)Relied on for: Marine forecasting including sea state, swell, wind and the interpretation of shipping and inshore waters forecasts.States this directlyCitation checked — the work exists and is described correctly
Where to go next
Related reading
What these connections rest on (1)
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Reading the tide
A mechanism edge from a record to the reasoning beneath it, resting on shore-fishing practice reported consistently across independent practitioner sources rather than on experiment.
- NOAA Ocean Service tides and water levels educational tutorial — National Oceanic and Atmospheric Administration, United States (Government fisheries body)Relied on for: Public education on tidal generation, the semi-diurnal cycle, spring and neap tides, datums and predicted tide heights.States this directlyPassage read and verified
- Met Office shipping forecast, inshore waters forecast and marine warnings — Met Office, United Kingdom (Government fisheries body)Relied on for: Marine forecasting including sea state, swell, tidal stream information and the interpretation of inshore waters forecasts.States this directlyCitation checked — the work exists and is described correctly
How this compares
- Depth and length: fathoms, metres and feetBoth records are about numbers that mean less than they appear to: one is exact and frequently misread, the other is a prediction that wind and pressure regularly beat.
- Moon phase and fishingSprings and neaps are a lunar cycle, which is why a great deal of what is attributed to moon phase in tidal water is a tidal effect wearing a lunar name.
- Reading a tide for fishingThree tide records doing three jobs: how tides work, what the published numbers mean, and which state of the tide actually fishes. Conflating the second and third is the commonest tidal mistake there is.
What these connections rest on (3)
Practitioner consensus — 3 connections
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Depth and length: fathoms, metres and feet
Two records a reader is deciding between, joined so that the trade is visible from either side.
- Angling Times — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK coarse, match and lure angling practice as reported by practitioners, including tackle convention.States this directlyCitation checked — the work exists and is described correctly
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling practice as reported by practitioners, including tackle, bait and lure convention.States this directlyCitation checked — the work exists and is described correctly
Moon phase and fishing
Two records a reader will hold in mind together, joined where reading both is what makes either usable.
- NOAA Ocean Service tides and water levels educational tutorial — National Oceanic and Atmospheric Administration, United States (Government fisheries body)Relied on for: Public education on tidal generation, the semi-diurnal cycle, spring and neap tides, datums and predicted tide heights.States this directlyPassage read and verified
- Met Office shipping forecast, inshore waters forecast and marine warnings — Met Office, United Kingdom (Government fisheries body)Relied on for: Marine forecasting including sea state, swell, tidal stream information and the interpretation of inshore waters forecasts.States this directlyCitation checked — the work exists and is described correctly
Reading a tide for fishing
Two conditions records a reader will weigh against one another, joined where the contrast is what makes either usable.
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling practice as reported by practitioners, including tidal timing and shore conditions.States this directlyCitation checked — the work exists and is described correctly
- NOAA Ocean Service tides and water levels educational tutorial — National Oceanic and Atmospheric Administration, United States (Government fisheries body)Relied on for: Public education on tidal generation, tidal streams and the relationship between water level and flow.States this directlyPassage read and verified
Safety reading
What these connections rest on (1)
Authoritative guidance — 1 connection
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Tides and being cut off
A hazard characteristic of the ground or the practice, joined to the topic that treats it in full, on guidance published by water safety bodies.
- RNLI water safety guidance: cold water shock and Float to Live — Royal National Lifeboat Institution (Water-safety or diver-training authority)Relied on for: Water safety guidance including tidal cut-off, cold water shock and the circumstances in which coastal users get into difficulty.States this directlyPassage read and verified
- United States Lifesaving Association public education on rip currents and the surf zone — United States Lifesaving Association (Water-safety or diver-training authority)Relied on for: Public education on rip currents, surf zone hazards and the circumstances in which people are swept from shorelines.States this directlyCitation checked — the work exists and is described correctly
Sources for this page
- NOAA Ocean Service tides and water levels educational tutorial — National Oceanic and Atmospheric Administration, United States (Government fisheries body)Relied on for: Public education on tidal generation, the semi-diurnal cycle, spring and neap tides, datums and how predicted tide heights are produced.States this directlyPassage read and verified
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK sea angling practice as reported by practitioners, including shore technique, terminal tackle, bait and species behaviour.States this directlyCitation checked — the work exists and is described correctly
- Met Office shipping forecast, inshore waters forecast and marine warnings — Met Office, United Kingdom (Government fisheries body)Relied on for: Marine forecasting including sea state, swell, wind and the interpretation of shipping and inshore waters forecasts.States this directlyCitation checked — the work exists and is described correctly
How FishingHQ labels evidence is explained in the evidence policy.