World's strand, sway of the sea

I lie awake. The only sound, regular loud thuds beating a steady rhythm. I'm taken back to my childhood, lying in bed listening to the sea beating against the shore. But in the quiet London night what I'm hearing, I realise, is my own blood flowing, too loud for me to sleep for a long time. Then later, I don't hear my blood any more, but instead (something of which I was previously unaware) the insistent ticking of my small bedside clock.