Steve Haycock and Wendy Lee, from Colchester, Essex, travelled to Unawatuna, a village on the island's southern coast, with a party of 38 friends and relatives, including seven teachers.
On Boxing Day morning the couple were in bed when they heard screams coming from the nearby beach. They watched in disbelief as the wave swept away Mr Haycock's brother and his girlfriend, eventually pinning them against the floor below. Mr Haycock and Ms Lee frantically tied together bedsheets to save them, until someone on the floor below reached over the balcony and pulled them to safety.
By nightfall all of the wedding party was accounted for, with the exception of fellow Colchester teachers Adrian Howells and Dunica Lintner.
The wedding party, which was being looked after by a Sri Lankan family in the hills, prepared for the worst news about their two teacher friends. Mr Haycock, said: "I really thought we would be looking at their bodies in the morning."
They found Mr Howells, a science teacher, at Philip Morant, and Ms Lintner, a PE teacher at Sir Charles Lucas, sheltering on another part of the mountain the next day. Mr Haycock, said: "It is remarkable that we are all safe and well. You almost feel guilty."
Now home, the couple are still having trouble sleeping and were off school for a week recovering from their ordeal. They plan to marry in Essex later this month.
Miss Lee said: "The wedding seems insignificant now but we had already planned to have a wedding reception at a hotel here to celebrate with all our friends and family at home: it will now also be a survivors' reunion."
The couple have vowed to go back next Christmas to make sure their Sri Lankan friends are OK.
Anyone wishing to give to the Unawatuna Trust Fund can do so at any HSBC branch quoting account number 51344110,sort code 402815.