I spent a decade or so living on and exploring the northern section of the Niagara Escarpment.  The limestone escarpment was everywhere, from towering cliffs off in the distance to the rock just inches under the soil of your front lawn.  Where the escarpment interacts with the waters of Georgian Bay you will find these rounded off pieces of limestone.  I suppose their shape has something to do with the waves.  I never thought much on how they became so boulder-like.  I was fascinated with the shape, texture and colour of these rocks.  You need  at least a couple hours (preferably half a day) to study the limitless combinations of compositions.  If you get a little stiff from bending over looking at rocks, you can always go for a swim in the refreshing waters of Georgian Bay or (as my wife did) suntan and read a book.