Jennifer Lopez Strips Down Naked For Bubble Bath

Jennifer Lopez knows how to make a big splash ... especially when she's completely naked inside a bathtub!

And that's exactly what J Lo showed the world Sunday in a series of photos posted on social media ... she's nude in a bubble bath with her sister, Lynda, sitting nearby.

Both are chowing down on something scrumptious and seem to be having a blast ahead of J Lo's upcoming 57th birthday ... but Lynda's the only one wearing clothes.

J Lo's birthday is Friday and her sister turned 55 last month ... ao she captioned the post, "A double birthday sister trip is always a good idea!! I love you Lynnie!! Happy birthday!!"

The photo dump includes a bunch of other photos showing J Lo having fun overseas with her sis and friends ... with photo shoots, fashion shows, fancy desserts and sporting events among the highlights.