"...Far below the girl on the rocks, but all too close to Ned, the tide was creeping in. Unable to take her eyes off the breaking waves, Jessica had a sense that the sea was taunting her. She'd see two, maybe even three, small waves in succession and tell herself that maybe the tide had peaked, that it didn't always reach exactly the same height every day. There were high tides and low tides, weren't there? Well, maybe this was a low tide and Ned wouldn't even get wet. There was plenty of time for help to arrive.
And then a massive wave would strike, dwarfing all that had gone before, and surging ever higher up the beach towards her unconscious brother."