It's the summer of sharing, as people seeking a taste of the luxe lifestyle book everything from boats to swimming pools on flourishing, Airbnb-style rental marketplaces.

Why it matters: People can increasingly rent the lifestyle they desire for a fraction of the cost of ownership. That's created a cottage industry for entrepreneurs to manage their own mini-fleets of rental cars, boats or homes for listing.

The big picture: Fifteen years after Airbnb debuted as a cheap hotel alternative, peer-to-peer sharing is established in our culture. You can now rent someone else's home, car, swimming pool, backyard, private tennis court and more.

• Pool-sharing site Swimply, for example, has boomed amid the pandemic. It has hosted more than 150,000 bookings on its platform this year, up from just 800 in 2019, a spokeswoman says. It's now planning to add tennis courts, private gyms and more.
• Explore Eden is building an online marketplace to connect campers with private landowners.

Driving the news: Miami-based Boatsetter this week raised $38 million to expand its business, which counts 50,000 boat listings in 700 locations worldwide and aims to reinvent the $60 billion boating industry.

• The Series B round was co-led by Level Equity. Reddit co-founder and entrepreneur Alexis Ohanian is also an investor, along with Certares.

Details: Boatsetter, co-founded in 2014, matches boat owners with people who want to get out on the water.

• Users can rent boats by the hour or day — or grab yachts for longer luxury vacations.
• Inexperienced boaters can hire licensed captains.

Of note: Unlike other watercraft rental companies (like GetMyBoat), Boatsetter is the first to offer peer-to-peer boat rental insurance, says Jaclyn Baumgarten, co-founder and CEO.

• "The No. 1 challenge I had to solve was insurance," Baumgarten tells Axios, noting that most recreational boat insurance policies are voided if the owner rents out their vessel.

What we're seeing: Peer-to-peer sharing is becoming more professional and less about earning a little extra cash to offset the cost of your car or boat.

• Airbnb's founders started out renting air mattresses on the floor to offset their rent, but many of its listings are now owned and managed by real estate professionals.
• That's true at Boatsetter, too. One Miami-based captain, for example, lists six boats for rent and nets about $100,000 annually from her charter business, says Baumgarten.
• The same is happening at peer-to-peer car rental site Turo, where one Miami entrepreneur lists 22 vehicles for rent, often packaging them with Airbnb properties he also manages. He told Axios he can pocket a $30,000 profit in a good month.

A different business model comes from Kindred, a members-only home-swapping network that started among a group of friends seeking a change of scenery for remote work during the pandemic.

• It's a "give-to-get" model: You earn points toward booking a place by renting out your own home.
• Membership is $300 a year and entitles you to rent other members' homes for about $30 a night — far below a typical hotel or Airbnb. Longer stays are cheaper, and cleaning costs are extra.
• "Psychologically speaking, there's something nice about knowing that everyone staying in your home has also listed their home on the platform," says Talia Goldberg, a partner at Kindred investor Bessemer Venture Partners. "There's a level of trust; I want people to respect my home, just as they want someone to respect theirs."

The catch: You have to be "accepted" as a member while Kindred matches supply and demand. Right now, Kindred lists over 500 homes across 20 U.S. cities.

The bottom line: What's mine is yours — for a fee — in the new sharing economy.