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 Moon is in conflict with those who are ruled by Mars, and Mars is in conflict with those ruled by the Moon. - Picatrix (Andalusia, ~1000.AD)