Most are remarkably deep for their size and bowl shaped from their sandy composition. Twenty five feet of depth in a twenty acre pond is usual and forty not uncommon. Long pond in Harwich is seventy five feet deep. A few ponds are dammed marshes. These may be large by Cape standards but only a few feet deep.
Ponds connected to the ocean are the most fertile.
This is because of the anadromous fishery that influences them. Alewives and american eels migrate to these ponds to spawn or mature and then contribute to the forage base and balance of the freshwater fishery. Back to fishing. The next good look you should take is the deep view. If you have a depth dounder, all the better.