I found the melody and words of this song in a little book called The Chime Child, written by Ruth L. Tongue. It is a collection of songs from the Somerset singers.
Apparently there was a custom in England that sailors or fisherman were not allowed to be buried in the churchyard like other folks, because the townsfolk were afraid that the seas would "come looking after them," thereby taking a considerable part of the rest of the town when it found them. So for a long time, sea-faring men were buried below the hightide line. Later they relented of this practice and decided that if they only buried their boots below the hightide line the sea could find them quite easily, and be satisfied with that.
The waters they washed them ashore, ashore,
And they never will sail the seas no more.
We laid them along by the churchyard wall
And all in a row we buried them all,
But their boots we buried below the tide
On Severn-side.
The gulls they fly over so high, so high,
To see where their bodies all safe do lie;
They fly all around, and loud they do call
All over the place where we buried them all,
But their boots we buried below the tide
On Severn-side.
Brean Lament is recorded on the album Ensemble