A lake in a dream usually reflects a calmer, more contained emotional state than an ocean or river -- feelings you've found some stillness with, at least for now. A clear, quiet lake can point to unhurried reflection and inner peace, while murky or disturbed water may suggest that stillness is more fragile than it looks.
The qualities of Saturn and Mars are not made better by their Conjunction; being mixed so together, they are confounded, and hurt very much. - William Lilly (1602.-1681.)