Fences, gates and covers can all be useful safety precautions — but they’re most effective when the homeowner deploys and maintains them in accordance with the manufacturer’s recommendations.

This points back to a more fundamental issue: That the most crucial layer of protection for any pool is vigilance.

“The topic we come back to again and again with our customers is that the number one layer of protection is adult supervision,” says Matt Mossman, owner of California Pool Covers Services Inc. in Anaheim, Calif.

To illustrate his point, Mossman tells the story of a customer — a mother of young children, who called and told him, “You’ve got to get out here and fix my pool cover, because I don’t trust my nanny with my kids.”

“What can you say to that?” Mossman says. “You’re depending on your automatic pool cover to keep your kids safe because you don’t trust your nanny?”

In short, no fence or alarm is as effective as simply paying attention, or finding someone who will.