Lakes are a common concept in the Yellow Mythos, with Lake Hali and Lake Demhe. In The Repairer of Reputations, it is said that lakes connect Hastur, Aldebaran and the mystery of the Hyades (and that understanding this link somehow empowers one to rule).
See also Lake bed.
Ponds[]
Sometimes there isn't room for a lake, but a pond may appear to fulfil a similar role, such as in A Christmas In Carcosa.