The photo showed Bella with her back turned to the camera wearing a blue dress as she stared out towards the ocean.
"'For whatever we lose (like a you or a me), It's always our self we find in the sea,'" Bella wrote in the caption, quoting American poet E.E. Cummings.
Bella announced the breakup on Sunday. The two had been together for six years and officially engaged ever since Cena proposed during the WrestleMania 33 event in April 2017. The two had a wedding planned for May.
"After much contemplation and 6 years of being together Nikki Bella and John Cena announced today their decision to separate as a couple," the statement read. "'While this decision was a difficult one, we continue to have a great deal of love and respect for one another. We ask that you respect our privacy during this time in our lives.'"
Sources close to the couple claim Bella was the one who pulled the plug on the relationship. One source told PEOPLE that she was "convinced" Cena had changed from his policy of never wanting to get married or have children.
"When [Cena] proposed, he convinced [Bella] that he was a changed man. And if he can change his mind about never wanting to get married, why wouldn't he change his mind about not wanting kids?" the source said. "They have had an on and off relationship for years. It's no secret that they didn't see eye to eye on a lot of things, but, when you're in love, you turn a blind eye. And that's what Nikki did,
"When Nikki changed her stance about wanting kids, everyone knew that wasn't her. You can't take motherhood away from a woman," the source added.
Cena has not been on WWE television since his quick loss to The Undertaker at WrestleMania 34 on April 8. Aside from a number of Instagram posts potentially related to the split, the Blockers star has remained silent.
He did however reveal in an interview with Us Weekly a month before the split that he and Bella would go months without seeing each other due to their busy schedules.
"Anytime I get upset, I always just realize that I can't live without her and I love her and that's why I cave in on a lot of stuff. It takes being able to mesh two lives," Cena said. "She's super busy and sometimes we don't see each other for months at a time, but when we do see each other, it's our time and it's our time together. I think, for now at least, that is certainly what's making this work."