How does Lessing's word choice help readers experience the danger of what is happening in "Through the Tunnel"?

One way that readers understand the danger posed to Jerry at the "wild and rocky bay" is through Lessing's word choice. Once Jerry gains some independence from his mother and goes to his own beach, he spies "inlets of rough, sharp rock," and says the choppy surface of the water looked like "stains of purple and darker blue." Words like rough and sharp sound painful, and stains of purple and blue sound like a description of bruises, which are also painful. As Jerry swims out further, he sees "rocks [that] lay like discolored monsters under the surface," and "irregular cold currents from the deep water shocked his limbs." The simile that compares rocks on the bottom of the ocean floor to strange monsters is certainly ominous and concerning, conveying a sense of the danger here. Further, that Jerry's body can be "shocked" by unforeseen cold currents also implies a danger and lack of predictability on this beach.