A stretch of time where the water sits above, or below, a height you need. Deep enough to launch, shallow enough to wade, whatever your trip requires. Instead of reading raw high and low times, you give the planner your height and your available hours, and it finds the days that fit.
Mean Lower Low Water. It's the average of the lowest low tide recorded at a station each day, measured over a long-term reference period. It's the standard datum NOAA uses for tide predictions in the US, and every height on this site is measured against it. A prediction of 1.0 ft means one foot above that baseline, not one foot of actual water depth. What's under your keel depends on the charted depth at your spot plus the tide height.
A reference station has its own long-term tide gauge and a full set of harmonic predictions. A subordinate station has no gauge of its own. NOAA derives its predictions by applying a time and height offset to a nearby reference station. Both work the same way here, and each result is labelled so you know which you're looking at. It matters because subordinate stations only publish highs and lows, never an hourly curve, which is why this site interpolates between them.
NOAA's astronomical predictions are generally reliable days and weeks ahead, but they account only for the gravitational pull of the sun and moon. Wind, atmospheric pressure, and heavy rain runoff can push actual levels higher or lower, sometimes by a foot or more. A sustained onshore wind piles water up; a strong offshore blow can empty a bay well below the prediction. Treat the planner as a starting point and check conditions before you go.
NOAA gives us the time and height of each high and low. Between any two of them the tide follows a curve close to a half cosine, so we fill in the shape at six-minute steps and find the moment the water crosses your height. That's why a window might read 10:19AM rather than snapping to the nearest hour. It's an approximation of the real curve, accurate enough for planning and not a substitute for a gauge.
How fast the water is rising or falling, in feet per hour, worked out from the same curve. The moving water mode finds the stretch in each tide cycle where flow is above seventy percent of that cycle's peak, and labels it flood if the tide is coming in or ebb if it's going out. The peak figure lets you compare a strong spring tide against a weak neap at a glance.
Your station and height and hour preferences are saved so you don't re-enter them every visit. Dates are deliberately left out. They change every time you use the tool, so there's nothing to gain, and it keeps what little is stored to a minimum.
In your browser, on your own device, not on our servers. The privacy policy lists exactly what's saved.
Partly. Once installed, the app itself loads with no connection, and any tide data you've already looked up stays available. A station or date range you haven't fetched before still needs a connection, and the app will tell you when it's showing you a saved copy rather than fresh data.
On Android in Chrome, open the site, tap the three-dot menu, then Install app. On iPhone in Safari, tap the Share icon, then Add to Home Screen. On desktop Chrome or Edge, look for the install icon in the address bar.