Thanks, and apologies for jumping to conclusions! The only evidence of the pond I could find was a project to restore it in 2014 so I questioned its existence.

As for the beach, I think this extract from the wiki is relevant: natural=beach should only be used for inclined, wave formed areas at the coast. Larger flat areas of sand that are exposed at low tide should be tagged natural=sand + tidal=yes (and for muddy areas only, use tags natural=wetland + wetland=tidalflat).
So I would probably argue there isn't a beach around a pocket lake, but will defer to your judgement