Why do some cluster pins appear in the sea?
Map pins are clustered based on an arbitrary grid of squares – one grid per zoom level. All the pins in each square are grouped together into one ‘cluster’ pin which is positioned within the square such that it’s at the average position of all the pins it represents. Unfortunately, if the square happens to straddle a body of water where there are two river banks or shorelines that have pins on either side, the clustered pin may be averaged out to appear in the middle of the water.
