Speedsailing / bump and jump location. The wind comes in off the sea across the dunes and gives mirror flat water up to 30 foot off the shore. The trick is picking the flattest water (closest to shore) without getting into disturbed wind.
For speedsailing the best wind direction is SWW giving a broad starboard run just off the southerly shore, SSE is also good for a port run on the same shore but for some reason it's not quite as fast (mixture of gusty and water state).
In early spring the water is drained from the lake to allow breeding birds do their thing so it's really an Autumn and Winter location.
The bottom (southerly shore) is sandy with the odd shell encrusted rock that will tear your foot to shreds, just don't go tromping along the bottom thinking it's all sand, and you should be okay.