The size of Weller's Bay is 1852.4ha (4578ac or 18.5 sq km)
The Bay is hour-glass shaped and about 8 kilometers long, bounded by farm and residential land on the north, east and south and lovely sand beaches facing Lake Ontario on the west. A limestone promontory called Bald Head stands in the middle of the long sand beaches.
The most prominent feature of Wellers Bay is the strip of sand that separates the bay from Lake Ontario. The sand spit is known as a barrier beach, or baymouth bar. Technically, though, geographers classify Wellers Bay as a lagoon.
Many millennia ago, glaciers covered all of this area, where eventually the glaciers melted and they formed The Great Lakes. In the process, large deposits of sand were left behind. In Lake Ontario, the sand was eventually carried along by currents until it hit pre-glacial limestone outcroppings, which were remnants of ancient sea beds. Wherever these limestone headlands would appear, they would slow down the current and then sand would settle around the rock, eventually forming the large barrier beaches.
Today, the bay's bottom is composed primarily of sand and mud. The average depth is 2.8 metres (9′) and there are a lot of weed beds along the shoreline.