Is that on a dammed stream or a pond? College Woods comes to mind offering something like that.
It's 3/4 of a mile upstream from Wiswall Dam on the Lamprey River. Lots of kids play, swim, jump at the Wiswall Dam Bridge. But here 43.110046, -70.967750 is a water-intake pump house where UNH/Durham take water from the Lamprey and feed it into the Oyster River and UNH's water plant. There is a gated on-foot access from the Packers Falls Rd/Wednesday Hill Rd intersection. Nobody else goes here...