The greater the force that produces a wave, the greater the amplitude of the wave and the greater the energy carried by the wave. In a transverse wave the higher the wave, the higher the amplitude. Sounds with greater amplitude will be louder; light with greater amplitude will be brighter
The barnacles are only able to attach them selfs to surfaces in the water. Since the surface is limited, barnacles are attaching themselves to the other barnacles, crowding the rock. The muscles were not able to grow or attach themselves off the surface of the rock. Same thing with the mussels that are growing on the rock. So not only barnacles are crowding the rock, but Mussels as well are crowding the rock.