Up here in theNW ofthe UK we have a very large area of very flat open beach that is always revealed when the tide goes out called Pilling Sands, an awful lot of my initial training was carried out there simply because of the total lack of inhabitants who may complain of noise and intrusion.
I was allowed many times to practice landing and landings on targets(pick a spot) but it was drummed into me "If you land on sand below high water mark, do not Shut Down, and keep power pretty much at the point of lift off", two reasons were given,
1. Engine may not re-light,
2. Sand is not known for the ability to hold vibrating skids, which under certain conditions could sink very quickly due to Liquifaction( or water forced up to the surface) therby removing the load bearing property/capacity of the bit your skid's are on!
Sofar I have not landed and shut down on any beach side area!
PeterR-B
Vfr