An American man has drowned during an underwater marriage proposal that was recorded and posted to Facebook.

Key points: Steven Weber and Kenesha Antoine were staying in an underwater room at a Tanzanian resort

Steven Weber and Kenesha Antoine were staying in an underwater room at a Tanzanian resort Mr Weber proposed by pushing a note up against the window of their submerged bedroom

Mr Weber proposed by pushing a note up against the window of their submerged bedroom Ms Antoine posted on Facebook: "You never got to hear my answer, 'Yes! Yes! A million times, yes'"

Steven Weber and his girlfriend Kenesha Antoine were staying in an underwater room at the Manta Resort on Pemba Island, off the coast of Tanzania.

Mr Weber was recorded swimming outside the submerged bedroom, holding a handwritten note up against the window.

"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!" the note reads.

In the video, posted to Ms Antoine's Facebook page, he flips the page over to show the message "Will you marry me?" before pulling out a ring box and revealing the engagement ring inside.

Kenesha Antoine and Steven Weber recorded themselves in the underwater bedroom days earlier. ( Facebook: Kenesha Antoine )

Ms Antoine wrote on Facebook that Mr Weber "never emerged from those depths".

"You never got to hear my answer, 'Yes! Yes! A million times, yes'," she wrote on Facebook.

"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 cruelest (sic) twist of fate imaginable.

Steven Weber "never emerged from those depths", according to his girlfriend. ( Facebook: Kenesha Antoine )

"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."

"Wherever in the universe Steven's spirit now resides … he's probably entertaining someone with a story about how he royally screwed up that proposal and died while being extra," Ms Antoine said.

Manta Resort confirmed Mr Weber's death to the BBC, with resort chief executive Matthew Saus saying "everyone is shaken to the core".

CNN reported the US State Department confirmed a US tourist had died in Tanzania but gave no further details.

"We offer our sincerest condolences to the family on their loss. We stand ready to provide all appropriate consular assistance," the State Department was quoted as saying.