frank butler told me that he[frank] had played on tv as a seesion concertinist radio and mainly waterways programmes or programmes about canals, which do have a connection with things nautical.
here is an example of using concertina to accompany a sea song, the difference btween my playing and alfs, is that alf generally played the same accompaniment throughout the song ,it was rare[from my recolection for him to alternate between chordal playing and melody playing , although he did sometimes repeat the last 2 bars of a melody between verses.
http://www.youtube.com/watch?v=P1PaQaNH9NI