Found it! It's by Robbie O'Connell. (I think I heard him sing it a few years ago at the Mystic Sea Music Festival, in the boat shed.) The following is from Allyn Dimock:

I hope that people other than me are interesting in Robbie O'Connell's song "Before The Oceans Rose" I include the lyrics and a link to Robbie's performance (a very pleasant voice and good guitar accompaniment) below. Since it didn't seem like Robbie was about to record it, I got his permission to perform it and pass it on to interested people.

Before The Oceans Rose
(c) Robbie O’Connell, 2015, Slievenamon Music (BMI). All Rights Reserved.

Great grandad told me stories of when he was a boy,
How the world was different then and the freedom he enjoyed.
He spent his summers by the beach, in the winters that had snow,
but That was in the old days before the oceans rose.
They had football games and holidays, everyone had cars,
You could travel all around the world, there weren’t so many wars.
They had houses with big gardens where flowers and trees would grow,
(ch) but That was in the old days before the oceans rose
Way back in the old days before the oceans rose.

He told me how when he was young there was always food to eat.
Water wasn’t rationed. They had lots of fish and meat.
Where we have the desert now vast fields of corn were grown
but That was in the old days before the oceans rose.
They had festivals and carnivals, they had restaurants and pubs.
The houses all had showers then. Some even had bathtubs.
Oil cost more than water and you picked out your own clothes
but That was in the old days before the oceans rose
Way back in the old days before the oceans rose.

They had schools and universities, you could study what you liked.
You were free to pick your own job and you didn’t work the dikes.
Our leaders were elected then, you could vote for whom you chose
but That was in the old days before the oceans rose,
When the streets weren’t full of checkpoints, there were no I.D. tattoos,
They didn’t impose curfews and surveillance drones weren’t used.
You could wake up in the morning and just walk out of your home
but That was in the old days before the oceans rose
Way back in the old days before the oceans rose.

How could they have done nothing as the ice crashed to the sea?
As they watched the shriveled crops wither in the fields?
Its so hard to be hopeful when you see what’s gone before
back there in the old days before the oceans rose.
When profit is the driving force they don’t care what gets lost,
They can’t look beyond the balance sheet to see the final cost.
Profit isn’t everything as any kid now knows
as it was back in the old days before the oceans rose
Way back in the old days before the oceans rose.

No, profit isn’t everything as any kid now knows
as it was back in the old days before the oceans rose
Way back in the old days before the oceans rose.

Robbie’s rendition is at
https://drive.google.com/open?id=1772uwfzpJ33UfHpV4cCpVCV1iGSZWr90

(I think that the lyric is pretty much correct. I may have added or dropped the odd “then”. Robbie says of his performance that the tune for the last line of the first verse should carry through the rest of the verses of the song and only change for the repeat of the final chorus.)
Before The Oceans Rose.txt
Displaying Before The Oceans Rose.txt.