Backyard swimming has long been a summer staple, but as the cost of in-ground pools continues to climb, industry professionals say more homeowners are looking for alternative ways to cool off at home.

The new rule would affect nearly 1,000 shoreline properties. The 14 existing pools in the area would still be allowed.

Once dismissed as the cheaper, less attractive option, they’re now being integrated into decks, enhanced with landscaping, and designed to echo the look of in-ground pools. Quarter-wrap decks, which ...