In summer there are a lot of swimmers, but at the end of the day or if the weather is not that great it is not crowded. The water goes deep very quickly and with strong winds the water can be choppy. With the nearby harbor there can be waves when a boat comes by.
The beach is partly sand and partly grass. There's a beach specifically for surfers, but it is not ideal for launching your kite. You can better go to the swimmer beach, but be careful of the lines and poles in the water. Beyond the lines the water is clear for surfing.
The spot is only suited for kiting with a fairly strong wind. That's why probably only local surfers will go there, because if the winds are good here, they are all over the Netherlands.
If you take the A15 from Rotterdam to Nijmegen, take the second exit: Tiel, and go left. Now you are on the road to Mourik. Keep going strait ahead, also at three roundabouts. At the third roundabout, Mourik is indicated to the left, but go straight ahead. The next roundabout `Eiland van Mourik` is indicated to the left, follow these signs. Drive across the lake shore and park on the other side.