Slack-water alerts
A buzz twenty minutes before the stream turns, so you leave the pontoon with the tide instead of against it.
Tide prediction · 1,240 harbours
The moon
pulls.
We do the
maths.
Neap turns 37 harmonic constituents and the age of the moon into a tide table you can read from a wet cockpit: high water, low water and slack, to the minute, from Brest to Bergen.
LUNATION
Waxing gibbousILLUMINATED
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Waxing gibbousILLUMINATED
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Drag the moon through its month. The tide follows.
Range—
Next high—
Tides—
Port Calder,
next 24 hours
Heights above chart datum. Spring tides land about a day and a half after new and full moon, and Neap accounts for the lag, so the biggest range on this chart trails the brightest moon.
Surge offset
Pressure and wind from the shipping forecast nudge each prediction. A deep low adds water; Neap shows how much.
Offline tables
Twelve months of tables for every saved harbour live on the phone. No signal past the breakwater, no problem.