Simon Stratton, 32, asked Elinor Robson, 33, to be his wife during the annual World Bog Snorkelling Championship in Llanwrtyd Wells, Powys, The Mirror reports.
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He got down on one knee and said: "I'm bogging you to be my wife."
Simon chose the location as bog snorkelling is a favourite past time of the couple.
"I know a muddy bog isn't everyone's idea of romance but I knew she'd say 'Yes'," he said.
Elinor added: "I never thought that when I got engaged it would be in a bog."
The couple had more reasons to celebrate as they both took home bronze medals from this year's championship.
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