I went to France last week, to Finisterre in Brittany. The Bretons would maintain that they are not really French at all, but their own nation, which teye are, culturally. I saw lots of Breton language signs, and if I said them out loud I could see the connections with Welsh. The Breton name for Finisterre (which translates as end of the earth in English) is Pen ar Bed. Welsh for end of the earth would be Pen y Byd. If you say both names out loud, they sound almost the same... and just like the Welsh, the Bretons are fiercely proud of their language and cultural heritage.
I visited lots of absolutely beautiful churches, every little village seemed to ahve one grand enough to be a cathedral in other places, and many had carvings which showed how previous cultures/religions had been incorporated into the new religion. And of course, having such an extensive and very dangerous caostline, there is also evidence of their belief in sea creatures. Here are a few pictures taken at churches, which show what I mean.
Mermaids and sea monsters must have meant a lot to the people who built Sizun church, there are 7 mermaids carved into the stonework and several sea monsters.