I found 4 foot long fencing corner anchors at our local farm supply
store. They have an auger at one end and an eye at the other. I use
a 30" length of dowel rod to turn them into and out of the beach.
These have worked great on our 6000 lb 22 ft. cruiser that I beach on
the Mississippi sandbars. Wave action from barges and large cruisers
have not torn us loose yet. I beach the boat bow-first, set my lines
from the aft cleats on each side and run them into the beach at about
a 30 degree angle.