Jim Denevan, an artist and accomplished chef, creates immense pieces of installation art by making freehand drawings on sand. Armed with only a stick and no other measurement aids, Denevan can take up to seven hours to complete his transient masterpieces on wide, sandy beaches.
Snip from the site:
From the ground these environments are seen as places. Places to explore and be, and to see relation and distance. For a time these tangible specific places exist in the indeterminate environment of ocean shore. From high above the marks are seen as isolated phenomena, much like clouds, rivers or buildings. Soon after Jim’s motions and marks are completed water moves over and through, leaving nothing.
His site has a gallery with many images of his impressive creations.