There's tide, because it's a spot at North sea. The water is flat when you stay between the sand banks, and there can be some waves in the deeper water. It isn't a shallow spot, because it's at sea, but when you stay between the sand banks it can be fairly shallow.
Sandy beach. There are some shells on the sand but not much. There is room enough to safely launch your kite. With high tide however the beach becomes somewhat narrow. Entry: Take the entry at the parking lot below the viaduct, not the parking lot where the wind-turbines are. Because it can be crowded there with tourists.
Summer (May till mid September): water 14-20°C, air 15-25°C. Cold period (October till April): water 5-8°C, air in average 5-12°C, but can be sub zero as well. Wetsuit always recommended, winter drysuit or 5mm.
The wind is solid here (for Dutch standards anyways), and blows mostly out of Southwest till Northwest. The wind speeds vary from 8 knot days on hot summer days to 25 knots in autumn. Avg: 10-18 knots.
From the Randstad (Amsterdam, Rotterdam, Utrecht): Rotterdam-Benelux tunnel or Brienenoord Bridge. Follow the directions for Zierikzee (A15-A29-N-59). After Zierikzee follow the directions for Burgh-Haamstede. Before reaching Burgh-Haamstede, take the exit Westenschouwen/Middelburg (N57). Follow the signs for Neeltje Jans, and after that the signs for WaterLand.
It is OFFICIALLY ILLEGAL to kite there, so be warned. However you may kite there if you behave well, if not kiting could get definitivly banned from the spot!