He has a perfect scene of menace. Perfect because it's so underplayed. Our imagination is much better at filling the blank than words would be (it is set at a beach, where a nameless women's two young boys are building a sand castle when she decides to go for a quick dip).
She swam against the grain of the ocean, using a short and sharp stroke and a smooth kick.
She did not see the murky shape drifting toward her. It was more than half-submerged, and it had eyes. When she barged into it, the silent mass reared up.
Her scream was muted, most of it locked in her throat.
On the beach, her sons threw sand at each other and the man with the device unearthed a nickel. The lifeguard rearranged his legs in a way that the girls below could see the filled harness under his neon swim trunks. A stray cloud blotted some of the sun.
One of the boys pointed with his shovel. "Look at Mommy."
And that's about it, except for the lifeguard finally noticing. I love the dramatic irony of the beachgoers being completely unaware of what's happening mere feet from them, the child not understanding what he is seeing. Giving us a close up of what the shark is doing would have taken the edge off. My imagination fills in the blanks much better than the writer could.
It's why the monster is always so much scarier when he is still under the bed.