Lake or Marsh means ‘open’ or ‘loose’. It can be literal: the cart losing its axle strap. As part of a hexagram it means opening up to others, to exchange, to interact, to relax together. As ‘marsh’ it is the breeding ground for all species, for all connections, for love and hate, joy and disappointment, for storytelling and magic.
When Lake is below or inside, it has to do with your inner conversations. Are you easy and relaxed when in standby, or worried by default? It will show to the outside as a positive or a negative attitude, the half full or half empty glass. Lake is also social interaction, the need to be part of a whole, to not be alone, and to build a strong community together.
An inner excess of Lake can cause depression or superficiality, both due to an inability to find your own meaning in life, or rather an inability to trust it has.