We found huge sections of the beach with these rock patterns
We went for a lot of beach walks on the east coast of Tasmania, and we came across this phenomenon more than once. It’s rock, but it looks like paving stones on a street.
These are not separate stones! It is one big rock!
The ocean and the wind does creates a nearly perfect grid system that makes the rock look man-made…but it’s all Mother Nature. It’s called tessellated pavement.
The grid lines are almost perfectly straight
The Parallel Life 
seriously mother nature does not create perfect right angles
I guess I would argue that none of these are exactly right angles…though they certainly are very straight in some places. Nature does indeed create some pretty spectacular angles though, the most common examples I can come up with off the top of my head are snowflakes and crystals, particularly the salt crystals that are formed in places like the huge salt flats in Bolivia and northern Argentina. They are spectacular, just google image it, or better yet, hop on a plane and go check it out yourself. Here’s the write-up from the national park about the ‘tessellated pavement’ since you seem skeptical. http://www.parks.tas.gov.au/file.aspx?id=7038