The point is that GPS SYSTEM, though phenomenally accurate MOST of the
time can fail SOME of the time.

More likely your unit wasn't picking up enough satellites. This is not the
fault of the GPS system. Some older units didn't do a very good job of
pickup up sats when there's overhead leaf canopy (some still don't). Don't
blame the system for inferior equipment.

An anchor watch in open water, without high terrain or foliage nearby, will
likely be very consistent in it's location.

If you are interested I took a picture of my plotter which I posted here.
http://ph.groups.yahoo.com/group/sho...os/browse/bd9e

Which is a useless link unless someone joins that group. Try using a free
service like flickr instead of forcing people to join (and presumably then
leave) a group.