i'd say
when the sand was out the range of the water/moisture, say half a mile
(
Dr. Kitteny Berk almost certainly drunk,
Sun 3 Aug 2003, 11:34,
archived)
The crux of the issue being
it simply never happens, so is 100% of hypothetical.
(
supermoore: HUNG,
Sun 3 Aug 2003, 11:37,
archived)