Jennifer Lopez and Alex Rodriguez are doing it BIG in Capri -- partying on a superyacht with billionaire Miami Heat owner Micky Arison ... proving once again, it's great to be rich!
J Lo and A-Rod took a smaller boat over to Arison's legendary Sirona III -- a 185-foot floating palace that fits 12 guests in 5 state rooms.
It's got a hot tub on deck, a sick bar area, a gym and plenty of deck space to take in some sun while sipping on boat drinks (shout out Jimmy Buffett).