"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," wrote Kenesha Antoine on her Facebook page after her boyfriend Steven Weber proposed to her underwater and "never emerged from those depths." 

Weber and Antonie were staying in a submerged cabin at the Manta Resort, off Pemba Island. On the third day of their stay, Weber dived under water to ask Antonie to marry him with a handwritten proposal note against the cabin window as she looked at him from within.  

Afterwards, Antoine confirmed his death in a Facebook post. And the Manta Resort said in a statement that "it is with the deepest regret that we inform that a fatal accident occurred at The Manta Resort on Thursday 19 September, 2019." 

Matthew Saus, CEO of the resort, said the team responded to a "problem in the water," but "absolutely nothing could be done" when the staff arrived. 

The couple booked four nights at the resort's underwater room, which is about 250 meters from the shore, in Tanzania. On the third day of their stay, Weber, from Baton Rouge, Louisiana, plunged into the water to make his proposal. 

He was wearing goggles and flippers in the proposal video, and holding a note against the cabin's glass window 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!" 

"Will you please be my WIFE," the note continued. "Marry me???" 

The footage shows that Weber turns over the paper sheet to reveal the proposal, pulling an engagement ring from his shorts and then swimming out of view. 

The Manta Resort told the BBC that Weber "tragically drowned while free diving alone outside the underwater room" on Thursday. 

In a Facebook post, Antoine said Weber would "never got to hear her answer" to his proposal, which would have been "a million times, yes." 

Local authorities are investigating the case, and the U.S. Department of State said it is aware of the death of a U.S. citizen in Tanzania.