The ocean disappears, people suddenly hear rushing water

"A Stay at the Ocean" by Robley Wilson Jr (1930-2018), first published in the Summer 1969 issue of The Carleton Miscellany, a literary magazine published by Carleton College in the 1960s and 70s.

I also remember reading this story when I was in 7th grade (1973-74) but could not remember the title. A Google Search brought me here a few months ago. The detail that stuck with me was the end of the story where the father worries about the salt corroding the car. Anyway, I tried some more remembering and searching, and if you don't care how I finally found the answer, go to the end of this post.

What I also remembered was that the story was not in our normal text (Projection in Literature) but in a medium-sized, white, soft-cover book with a drawing on the front. I (mistakenly, it turns out) thought it was a science fiction book because I also remembered reading a story about someone who went back in time to kill a dinosaur and changed the course of history because he stepped on a butterfly. I didn't remember that title, but it was easy to find ("A Sound of Thunder" by Ray Bradbury), so I thought I'd look for collections that included Ray Bradbury stories. Yeah, that wouldn't take long. As luck would have it, though, I found an index page on Google Books that listed all the collections with "A Sound of Thunder," including one promising collection titled Eco-Fiction by John Stadler, published in 1971. I found a table of contents and bingo, I remembered we also read "The Birds" from that book. But seriously, I also found the answer to the question.

"Makes you feel like Davy Jones, doesn't it? I looked into that hatch down there. Couldn't see anything, but I could hear water sloshing. Bet there's a lot of bones rolling around in there poor bastards." Stephen nodded. He didn't feel like talking, but stayed on the ship, bracing himself against a ventilator. To be above the ocean's floor was pleasant; the air was warm and windless; he even enjoyed the difficulty of keeping his balance, after hours of cramped driving. Certainly, this had been the most remarkable day of his life — of all their lives — and filled with small wonders. The lobsterman pulling his coaster wagon. The foolish couple from Iowa with their shovels and dreams of treasure. The boy and girl at the cliff, acting like honeymooners picking edelweiss in the Alps. And the ocean. The ocean he had grown used to in summer after summer of holidays in Maine — suddenly turned into a desert. Still, he felt a faint shiver of apprehension. If there was water in the hold of this broken tanker — He edged his way to the open hatch, a gaping black hole in the rust and scale of the deck-plates, and tried to see inside. It smelled like ocean, he thought. He listened, and could hear the water. Why should it be moving? Stephen stepped off the hulk and looked around. Nothing— but was that fog, far off to the east. Stephen called up to the man in Bermudas.
"Do you hear anything?"
"No," the man said.
Stephen noticed a car about a mile away, headed west. "Wait a minute," the man said. "I do hear something."
It was the sound he had awakened to that morning — of the tide, far, far out. "By George," the man said, "I think we've found her at last." He stumbled down from the deck. We've caught up with her," he said, and went to tell his family.

It ends with

"Daddy" The scream startled him. "Daddy, I can see it! I can see it coming after us!" Linda wasn't crying. In the rearview mirror, he could see her face, half-turned in his direction, her eyes vivid, her mouth working desperately to make more words. Out the back window he could make out a low gray wall that seemed to be gaining on him. Under his wheels he could hear water splashing, see spray flying. He switched on the wipers. He reached over and squeezed his wife's hand. At least we're all together, he thought. Off to the right he saw an overturned car, two men and a woman out trying to turn it upright. The sun was almost at the horizon and its light cast back a hundred rainbows through the wakes of a hundred cars. A pale, pebbly mist began forming on surfaces inside the car. The roar of the impossible tide was deafening; it seemed now to all around him, and the deepening water drummed like hammers against the metal under the car. He was thinking irrelevantly of how quickly the salt sea would rust out the fenders and rocker panels when he heard Clarice for the last time shrieking: "Drive, Steve, drive. For pity's sake, drive, drive, drive"