Hi Jean-Philippe,

I’m not 100% sure what you have in mind. It seems that the page you linked is showing the value based on different reference water level (tidal datum). The API is using MSL (Mean Sea Level) and it seems that the page https://maree.shom.fr/harbor/LANILDUT/hlt/6?date=2020-06-20&utc=standard is using LAT (Lowest Astronomical Tide) as reference water level. But even when I convert the value to use LAT as reference water level (by adding LAT to the value) the values are slightly off (like half meter or so). Also please note that the prediction is calculated using mathematical model which doesn’t take into account actual weather conditions and is calculated for place 5km away (you can check it using Marea website, which is using this API - https://marea.ooo/en/48.473738/-4.745571 ) . We are considering to add better predictions for places that have actual water level measurements available, but unfortunately for now we do not have any ETA for that…