The global supply chain is an intricate ballet of container ships, airplanes, trucks and trains. The coronavirus pandemic threw it out of whack. This is why you often can’t buy the goods you want.

Hot-tub maker Bullfrog Spas saw demand soar as homebound consumers upgraded their backyards. Yet its supply chain spans thousands of miles across continents and oceans. On a typical day, its Herriman, Utah, factory takes delivery of 40,000 gallons of chemicals, 400 sheets of plastic and up to 60,000 additional components.

“We have the best-case scenario on the demand side and the worst-case on the supply-chain side,” said Bullfrog CEO Jerry Pasley.

Covid-19 infections caused by the Delta variant are adding fresh uncertainty. Supply bottlenecks, especially at ports, continue to delay products of all kinds.

Bullfrog’s M9 spa is one of its most elaborate models. This shows how the company muddled through to get it shipped—most of the time.