When I built my pond, I had about 13T of 3/8" pea gravel spread to form a beach of sorts, an area for easy access in and out of the pond by either jon boat or by foot for swimming. The pea gravel is about 30-40' along the bank, and goes into about 2.5-3' depth of water.

The BG and HBG I stocked in mid March VERY clearly prefer this habitat, and I can see beds all throughout the pea gravel in as little as 12" of water.