The coastal environment, or littoral zone, is considered to extend seaward as far as the coastal environment, or littoral zone, is considered to extend seaward as far as the depth where storm waves can no longer move sediments.

The correct choice is that it extends until depths of around 60 m where sediments cannot move anymore. The important thing is that it certainly is not just the contact point of water and land; it goes into the sea until this point, where also enough light reaches the bottom for plants to do photosynthesis. D is wrong because breakers do not play a role in this definition, although it can vary from context to context (sea, lakes etc.).