Frequently Asked Questions

Tides begin with differences in the moon's and sun's gravitational pull across Earth. These forces drive repeating changes in ocean water levels. The moon has the stronger tidal influence because it is much closer, even though the sun is far more massive. Ocean basins and coastlines shape how that movement appears at a particular shore.

Tidal patterns vary by location. Some places usually have two high and two low waters, some have one of each, and others have uneven cycles. A calendar-day boundary can also leave a tide event just before or after the date you are viewing. Check the adjacent days rather than assuming an event is missing.

The moon moves around Earth while Earth turns. A location takes about 24 hours and 50 minutes, on average, to face the moon again. That helps explain why corresponding tides often occur later on successive days. The actual time shift varies with the local tidal pattern, so use the station's predictions rather than adding a fixed number of minutes.

Tidal range is the vertical difference between a high water and an adjacent low water. For example, a high of 2.4 meters and a low of 0.6 meters give a range of 1.8 meters. Both heights must use the same units and datum. Range describes how much the water level changes; it is not the water depth or a measure of current speed.

Spring tides occur throughout the year, around new and full moons. The sun's and moon's tidal effects reinforce each other, generally increasing the difference between high and low water. The name refers to the larger tidal movement, not the season. The largest local range does not necessarily fall on the exact date of the moon phase.

Around the first and third quarter moons, the sun's and moon's tidal effects partly offset each other. The result is usually a smaller tidal range: high waters are less high and low waters are less low than during nearby spring tides. Neap tides are a recurring part of the lunar cycle, not an absence of tides.

Tidal waves must travel through ocean basins and around coastlines, islands, and shallow areas. Bays and estuaries can delay, amplify, or reduce the water-level changes. As a result, places that are close on a map can have different tide times, ranges, or daily patterns. Choose a station that represents the waters you are visiting, rather than relying on distance alone.

King tide is an informal name for an unusually high tide, rather than a separate scientific type of tide. Such high waters can occur when astronomical and seasonal influences combine. The label alone does not tell you the predicted height or whether flooding will occur; check the local station and official coastal forecasts.

A closer moon has a stronger tide-generating effect. When its closest approach occurs near a new or full moon, it can produce a larger spring tide, called a perigean spring tide. That does not guarantee the year's highest water level at every station. Local tidal patterns, seasonal water levels, and weather also affect the result.

Search for a coastal town or station, browse the country and region lists, or select Find at the top of the page to look for nearby stations using your current location. Check the station’s name and map position before using its predictions. A nearby station may be in a different bay, inlet, or tidal system, so distance alone does not make it a suitable match. TidesPro identifies predictions by tide station, helping you see which location the data represents.

The day view focuses on one date. The week view helps compare successive days, while the month table and month chart show a longer pattern of tide times and heights. Use the date and view controls on the station page to switch between them.

Station predictions use the station's local time zone, rather than your device's time zone. Daylight saving time is applied according to that location's time-zone rules. When comparing TidesPro with another source, check the date, time zone, and daylight saving setting first.

Use the site's unit preferences to change how measurements are displayed. Converting feet to meters changes the units, but it does not change the tide's reference level, also called its datum.

Coverage depends on the station and its data source. A date outside the available prediction range, an inactive station, or unavailable source data can leave a gap. Try another date or check nearby stations, but do not assume that a nearby station has the same tide times or heights.

Read time along the horizontal axis and water height along the vertical axis. The peaks mark predicted high waters and the troughs mark predicted low waters. A rising curve means the predicted water level is increasing; a falling curve means it is decreasing. Check the chart's units and the station's stated datum when interpreting the height.

No. A tide height is measured above or below a reference level called a datum, not above the seabed. Water depth also depends on the seabed elevation. Do not treat a predicted tide height as the depth available beneath a boat.

A negative height means the predicted water surface is below the station's reference level. It does not mean negative water depth. Low water can be above, at, or below zero because high and low tides describe turning points, while zero comes from the chosen datum.

Check whether the sources use the same station, date, units, time zone, and datum. Different reference levels can give different numbers for the same water level. Prediction methods and source data can also differ. TidesPro lists station source and datum information where available; the tide datums guide explains the main reference levels.

TidesPro uses different sources depending on the station, including official tide services and predictions generated from tidal harmonic constants. Where available, TidesPro prioritizes predictions published by official agencies, such as NOAA. For TICON-sourced stations, TidesPro uses TICON-4 constants with the Slackwater prediction engine. Those are derived astronomical predictions, not official government tide forecasts. Check the source information on the station page for the location you are using.

No. A prediction estimates the tide; an observation measures conditions at a particular time and place. Wind, atmospheric pressure, river flow, and other local conditions can make the actual water level differ from an astronomical tide prediction.

No. Tide predictions alone cannot establish safe clearance, a safe crossing time, or safe sea conditions. Use current official charts, local notices, weather and marine warnings, and direct observations. Follow the advice of the relevant local authorities and allow for uncertainty in both water level and depth.

Use the Contact page and include the station name or page URL, date, time and time zone, and the value that looks incorrect. If comparing another source, include its link, units, and datum if known. Screenshots can help explain the issue; send them to the email address listed on the Contact page, as the contact form does not accept attachments.

No. Tide describes the vertical change in water level; current describes water moving horizontally. The timing of slack current can differ from high or low water and depends on the location. Use a suitable current prediction station rather than inferring current speed or direction from a tide-height chart.

These are solunar periods calculated from the positions of the moon and sun. Major periods are associated with the moon passing overhead or underfoot; minor periods are associated with moonrise and moonset. TidesPro shows them as planning information alongside tide and astronomy data.

No. Solunar periods are one planning aid, not a guarantee of catches. Species, season, habitat, water temperature, weather, and local conditions all matter. Use the fishing times together with local knowledge and the conditions at your fishing spot.

Yes. TidesPro has apps for Apple devices, including a Mac app. Visit the app pages for current features and download links. Website features and app features can differ, so check the relevant app description before purchasing. Eligible subscriptions include a free trial so you can explore the app’s features and decide whether it meets your needs. Check the subscription screen for current trial availability and terms.

Start with the Purchase Restore Troubleshooting page. Check that you are using the Apple account associated with the purchase. If you still need help, use the Contact page with your device model, operating-system version, and a description of what happens when you try to restore. Do not send passwords or payment-card details.

Visit the Widgets page to see the available tide and fishing-time widgets and get the embed code for your chosen location. Check the embedded station and display options before adding the widget to your site.