Silent tsunami at the closed Boardwalk library

"I was walking along a concrete boardwalk near an amusement park that looked like it had been closed for the winter, holding a rolled-up paper map of a city I’ve never visited. The sky was this heavy, uniform shade of slate gray, and the ocean out past the railing was completely flat and silent, like oil. Then the water line just pulled back really fast, leaving all these bare, dark rocks and dripping seaweed exposed in the mud. A few seconds later, this massive, dark wall of gray water came rising up over the horizon--no roaring or foaming top, just a huge, silent block of ocean pushing toward the shore. I tried to turn around and run toward the arcade building, but my sneakers kept slipping on loose gravel and my legs felt impossibly heavy, like trying to sprint through waist-deep wet sand. The water hit the seawall with a dull, heavy thud that rattled my teeth, and everything went cold and dark as it washed right over my head. Then I was suddenly sitting inside a quiet public library near the back window, staring at a display case full of old wooden clocks. My clothes were completely dry, but I had this overwhelming, cold knot of panic stuck right in the middle of my chest, and I couldn't stop looking out the window at the parking lot expecting to see the water coming around the corner of the building. Woke up taking a deep breath, clutching the blanket with both hands."