Why, when I throw a square shaped object into a pond.. the ripples are round...?

It isn't round.It is just that if all edges hit the surface simultaneously then the distance from centre through a corner any point on the cirference will grow at the same rate so after the wave has moved ,say,1m,the distance from object edge to wavefront as measured through the corners will only be the same distance in front of the wave which started from mid edge as it did at the Moment of splashdown.So in effect the wave will look circular only because distortion gets hidden by the coarseness of the wavefront.I stumbled on this explanation when some wimp of a teacher told me when I was about 10 years old that no matter what the shape of a mirror I would always see a circular image if I reflected the sun to a wall.Well I learned then that teachers only know what others have told them because a mirror close to the wall shows the shape of the mirror,the further away is the mirror the closer the image seems to approximate a circle.Try it,dont take my word for it!