What tides tell you—and what they don't

A tide table lists predicted high and low water times and heights for a location. A tide graph shows that rise and fall as a line. Dates or times run along the bottom; water height runs up the side.

Find the location first, then your trip date. Keep the time zone with the times: UTC is a worldwide time standard, not Louisiana local time. Some pages let you select local time instead. Check that choice before putting a high- or low-water time into your trip plan.

For Louisiana’s coast, NOAA’s Grand Isle station page is a research example. NOAA is the National Oceanic and Atmospheric Administration. Retain the actual station name/identifier, product, date and selected time zone rather than apply Grand Isle to every nearby marina or pond.

Read the product/legend so predicted heights/times are not mistaken for measured observations. Keep the station event time separate from page-access time. If you save an image or value, save its settings with it; a high/low time without date/time zone is incomplete.

A tide height needs a fixed starting level, like the zero mark on a ruler. The technical word for that reference is datum.

One common label is MLLW, short for Mean Lower Low Water. NOAA defines it from long-term low-water measurements. It isn't the bottom of the bay.

In an illustrative ‘1 foot above MLLW’ label, the height is one foot above that reference, not a one-foot-deep bay. A negative height is below the selected reference; it does not mean the whole area is dry. Preserve the sign, units and datum. NOAA explains tidal reference levels here.

Converting feet to meters changes units, not the zero or meaning of the height. Two figures in feet can still use different references. Do not combine a chart/sounder depth and station height as a shortcut to route clearance; those sources need their own context and appropriate navigation knowledge.

A prediction estimates the tide pattern. An observation is water height actually measured at a station. Wind and other weather effects can make the measured level different from the predicted tide.

Here's a made-up comparison: at the same station and time, the prediction is 0.8 feet and the observation is 1.1 feet. If both use the same units and reference level, the measured water is 0.3 feet higher than predicted at that moment. That difference isn't the water depth or a correction to add to tomorrow's tide.

Keep station, date/time/time zone, units and datum beside both values. Compare only matching settings at the same time; an observation from another hour or station does not supply the measured side of this example. Retain the measurement timestamp, not only when the page was opened.

If an observation is missing or old, leave that part unanswered. A predicted curve does not fill a measured-data gap, and an isolated difference does not establish its cause. The fictional 0.3-foot difference is neither bottom depth, a correction for tomorrow nor a measurement at another fishing position.

Depth is the distance from the water surface to the bottom at a particular spot. A tide station doesn't measure the bottom where you're fishing, so its height reading alone can't tell you whether a boat will clear a shallow area.

Current is water moving sideways—past a bank, through a pass or along a marsh edge. It affects where a bait or lure travels. High and low tide times don't have one universal relationship with the current at every location; NOAA's tides and currents FAQ explains the distinction.

From a suitable permitted position, observe natural floating material without adding anything. Record the visible path/place/time separately from the station prediction and observation. It is local surface movement, not measured speed throughout the water or evidence about the whole route. A high/low event does not guarantee slack water at that feature.

A bait or lure may move away from its cast’s landing point as line and water interact. Learn the intended movement/wait and return for one known setup before changing equipment. The reading-water article follows that observation sequence without claiming fish position or depth from it.

Keep three labeled entries:

• Prediction: station/product, date/time zone, event times/heights, units/datum and when retrieved.
• Station observation: matching settings and actual measurement timestamp/value, or still unavailable.
• Local visit: exact place/time, visible water edge or movement, access/source answer and unresolved question.

For an illustrative question, ‘How did the water edge and bait path differ from the last visit?’ uses the note without asking the tide table to measure that edge. A statement about local depth or usable access still needs separate support.

Across visits, keep the same station/reference/settings with the corresponding place and observation times. Compare what was recorded—edge covered/exposed, grass in water and the bait path—without assuming one visit establishes a fixed pattern. A prediction suggests expected level at its station; neither it nor an old local note confirms the exact edge, current or access today.

For a charter, ask which station/product concerns the actual plan, what level-related question the operator is reviewing and when any changed-service answer is expected. Use the separate marine-forecast guide for wind/waves; it does not replace these height records.

For your own craft, tide height alone does not establish clearance over a shallow place; appropriate local navigation information and skills remain separate. The measurements tool converts non-negative lengths only and explains why a signed source height must not have its minus sign removed to fit a form. Keep original values/settings and actual access answers with the plan.