Steven Weber and Kenesha Antoine's wooden cabin which they were staying in during their trip had a portion which was partially submerged, allowing the couple to observe under the ocean from their room.
A video showing Mr Weber swimming up to the underwater window wearing a snorkel and flippers while holding up a protected A4 sheet of paper to the glass which read: "I can't hold my breath long enough to tell you everything I love about you. But… Everything I love about you, I love more every day!"
Weber then unfurls the note, revealing the message: "Will you please be my wife? Marry me???" before pulling an engagement ring out of his pocket and then swimming upwards out of sight.
Ms Antoine then posted the footage on Facebook, saying "Yes! Yes! Yes!" in a seemingly happy ending. However, the engagement turned out to be short-lived when Ms Antoine revealed in an update that Mr Weber had died while underwater, writing he "never emerged from those depths".
She added: "There are no words adequate enough to honour the beautiful soul that is Steven Weber Jr."
"You never emerged from those depths so you never got to hear my answer, "Yes! Yes! A million times, yes, I will marry you!"
"We never got to embrace and celebrate the beginning of the rest of our lives together, as the best day of our lives turned into the worst, in the cruellest twist of fate imaginable."
"I will try to take solace in the fact that we enjoyed the most amazing bucket list experiences these past few days, and that we both were so happy and absolutely giddy with excitement in our final moments together."
Kenesha also described Steven as her "perfect love", her "angel" and her "soul", whom she would carry on loving forever.
"Rest well, my sweet baby! Always know that you are forever loved."
According to the Metro, an official said: "We offer our sincerest condolences to the family on their loss. We stand ready to provide all appropriate consular assistance."