Mariah Carey and James Packer have separate yachts: 'It's important to have his-and-hers everything!'

Most couples would be delighted to have his-and-hers bathrooms, but Mariah Carey and James Packer have taken things a few million steps further.

The engaged duo are currently enjoying a month-and-a-half long vacation off the coast of Capri, Italy – on their own his-and-hers yachts.

"It's important to have his-and-hers everything!" the 46-year-old singer told Entertainment Tonight while giving them a tour of her floating abode.

While Mariah relaxes on her own chartered 16-crew luxury liner, her Aussie billionaire fiancé, 48, parties nearby on his Arctic P, the seventh-largest privately owned vessel in the world.

The diva's 192-foot cruiser - which includes a gym, library, Jacuzzi, two bars, six staterooms, and a private chef - goes for the bargain rental price of $340,000 per week, plus expenses like $40,000 per week for fuel.

Still, that's just a drop in the bucket for a couple whose combined net worth is estimated at nearly $6 billion.

And while they may not have their own mini-yachts, Mariah's 5-year-old twins Moroccan and Monroe (with ex-husband Nick Cannon, 35) are lapping up the luxurious offshore life.

"They love swimming in the water," Mariah said. "They are amazing swimmers."

The family's extended holiday-at-sea – which has been on since early July - is set to end soon. Mariah resumes her Las Vegas residency at Caesar's Palace on August 24.