Matt Walker was swimming in Marine Lake, Clevedon, in August when the band slipped off his finger.
He contacted a metal detecting club who used their equipment to search the lakebed when it was drained last week.
Mr Walker said he would be "eternally grateful" to them for finding the white gold band, which is engraved with the date of the couple's anniversary.
He said: "I was swimming with the kids and when I climbed up onto a raft, I realised I had lost my ring.
"I was absolutely devastated to have lost it but the water there is so murky, there was no chance of finding it."
The "Somerset Artifact Seekers" - which helps people search for lost items - discovered the ring in the silt.
Volunteer Dave Baker said: "It took us about an hour of looking before I was minded to go over to the pontoon and then within seconds I found it.
"We do it because of that face they get when they see the item that they thought was lost forever returned to them- it is absolutely phenomenal."
Mr Walker previously lost the ring in a harbour in Cornwall, although was able to rescue it as the water was clear and it was easy to spot.
He said: "It's pretty careless of me really, I will need to get it made smaller."
His wife of 13 years, Rachel, added: "When my son told me Matt had lost the ring I thought he was having me on.
"I would have had a go at him as I always take my ring off when I swim, but he was really upset.
"We're so grateful to the group who found it."
Mr Walker has given the detectorists a donation by way of thanks.
A man has been reunited with his lost wedding ring after metal detectorists found it at the bottom of a lake.