We always try to plan the Kyocera Beach Challenge on a day and time that the tide is outgoing (the current is North to South) and not too long before low tide. This is optimal for both swimming and cycling. Below you can check the actual time of low tide for the coming Kyocera Beach Challenge (source: www.getij.nl). In case you want to exercise on the beach you can use this page to find out which time is best. Be warned: almost everywhere along the Dutch coast it is not allowed to cycle on the beach during daytime. In the evening and when the beach is quiet it is usually tolerated.
The sea water temperature during the Kyocera Beach Challenge is almost always more than 18 degrees. For the average sea water temperature in The Hague see the table below.