[Tagging] Beaches

[John Smith]

>From http://wiki.openstreetmap.org/wiki/Beach

> "Beach areas should always meet with a natural=coastline way. Do not use this tag for patches of sand/gravel which are not by a coastline. Note that the natural=coastline should ideally be positioned at the average high tide line, which may mean the beach is quite small or not mapped at all in fact."

By this logic wouldn't the beach cover from the average high tide line
to the average low tide line?

Which brings up the next issue, how to determine the average high and
low tide lines from aerial imagery...