Steven Weber dived under water with a message to his girlfriend asking her to marry him. (CGTN)

An American man drowned after proposing to his girlfriend underwater in Tanzania while on holiday there.

Steven Weber was in the East African country with his girlfriend Kenesha Antoine, with plans to ask for her hand in marriage.

The two were staying in a wooden cabin that had a partially submerged structure that allowed them to look under the ocean.

Reports indicate that Weber had dived under the water with a placard asking Kenesha to marry him, but never got back out.

The bride-to-be posted the sad news on Facebook saying that he “never emerged from those depths.”

Kenesha wrote: “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.”

The US Department of State confirmed Weber’s demise, but did not give any further information.