When does the
water go still?

The tide moves through the Oosterschelde like a long wave. The moment the current at a given spot becomes smallest doesn't always coincide with high or low tide from a standard tide table. That moment also differs per site. The planner therefore calculates with the expected current speed itself: a window is the period in which it stays below your chosen limit. For most windows we also show the moment the current is lowest. If the current direction doesn't clearly reverse there, we don't show a separate slack time. The calm window still stands as is.

Not every diver and every dive calls for the same amount of current. That's why you can choose a limit of 15, 20, 25 or 30 cm/s yourself in the planner. The planner uses that limit to show when the expected current is calm enough by your chosen value. The default is 20 cm/s, but this is not a safety limit.

The forecast is updated several times a day, but remains a prediction. Wind and water level in particular can affect the actual current and the moment it changes. The closer you get to your dive, the more up to date the forecast is. Always check conditions before entering the water.

Current and tide are important parts of dive planning, but not the only ones. Also check local conditions and specifics of the site beforehand, such as the entry point, shipping traffic, nature regulations and obstacles or oyster beds.

For the longer term we show an indication based on historical patterns. That lets you pick out a suitable day in advance. This indication is less accurate than the live forecast, because future weather conditions aren't fully known yet. As soon as a moment falls within the 40-hour forecast, the planner switches to the live forecast.

Water temperature is measured at Marollegat, one measuring point for the whole Oosterschelde. For a day in the future, we take the temperature from about a year ago on the same calendar day, and add the difference between today's temperature and last year's on the current date. Right after the 40-hour forecast that difference counts in full; further ahead it fades out gradually, to zero after about a month. It's an estimate based on the seasonal pattern and the current deviation, not a prediction.

Yes. Click "Plan this dive" on a dive window, or a slack time in the monthly overview. You only enter your email address and get your own page to share with your group. It shows what was planned next to what is expected now, with an alternative time. Anyone following the dive gets a message when the forecast changes, and afterwards a short question about the visibility. No account needed, and email addresses are deleted 30 days after the dive.