Thomas Mould, from Leicester, and American Sandra Hyde staged the unusual ceremony in the Florida Keys National Marine Sanctuary.
The couple, who have been together for four years, used an underwater tablet to exchange wedding vows beside Molasses Reef off Key Largo.
They had planned a summer wedding in an old English church but decided an underwater ceremony would be more appropriate and more cost-effective.
Thomas met Sandra in 2013 while on a dive trip with the Army in the Florida Keys, where she worked as an instructor.
The pair stayed in touch and visited each other a number of times in the US and UK.
The couple are on honeymoon in Florida and will return to England to live.
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