Rijkswaterstaat publishes quite a lot of information online. Water levels can be seen on a map[1] on waterinfo.rws.nl. It also offers access to historic data in CSV format, but that is handled through a wizard and you get the data by email apparently.

Information about sluices, bridges, etc. can be found on vaarweginformatie.nl, including the live status of many of them. The Ijmuiden sluice complex doesn't have a live status it seems. See [2] for the map.

[1]: https://waterinfo.rws.nl/#/publiek/waterhoogte [2]: https://www.vaarweginformatie.nl/frp/main/#/geo/map

I guess 99% of the population would not be qualified to tell if an open sluice gate is problematic under certain circumstances. If it were as easy as "Sluice gate open && water level > X" I am 100% sure there would already be an automation for it.