Sandspike- use a 1.2m piece of 50mm aluminium tubing-cut the bottom end at a large angle so that it tapers to a sharp edge on one side. You can do the same with pvc plumbing tube-this is lighter but you dont get such a sharp durable point. An option to enable you to push it deeper into the sand -which i use is to insert a crossbar of ss tubing-300mm long 15mm diameter-i insert this about 500mm up the aluminium tube -can be epoxied to the tube . The tube is best driven into the sand vertically