When Jim Battan spent $110,000 building a luxury pool outside his home in West Linn, Oregon in 2012, he knew he was making an investment.

He couldn't have known that 10 years later, he'd earn more than enough to pay it off by renting it out to strangers on the internet. Battan says that since September 2020, his pool has hosted roughly 9,000 swimmers through a platform called Swimply, which dubs itself the Airbnb of swimming pools. The result, according to documents reviewed by CNBC Make It: $177,000 in revenue in less than two years.