I went up to university in Newcastle in 1961, when most people spoke a far more concentrated version of Geordie than the smoothed-out version you hear today.
It didn't take me long to realise that the problem wasn't the accent, which I absolutely loved - and still do, it was the vocabulary. It was said then that Norwegians found Geordie easier to understand than English speakers because they had more words in common.
Perhaps if the cod were to take language classes.....
Having lived in Dundee for a while and had little trouble, I later was in Aberdeen for a year....and did get 'tuned in' by the end of that time, but not to some there who had a really broad accent AND dialect words. About my baby, in the street market: " Us ut a loonie 'r a quinie?".....yes I did get it, but he translated anyway, as I was obviously a Sassenach.
I can empathise completely with the Cornish cod. I find Scots (especially Glaswegian) and Newcastle accents a foreign language. Perhaps they should head around here to the East Anglian coast, my accent is always being confused with West Country.
The lady cod doesn't release her eggs until she's sussed-out the man cod but due to global warming and Cornish fish moving north they can't communicate well!
There are communication problems with mumbling and lack of consonant articulation as well. At risk of being shot down in flames (I'm used to it ? ), I think anyone who takes the trouble to speak clearly/not too fast can be understood whatever their accent. I often have to ask MrB and Minibags to just slow down their speech: one of them mumbles and the other speaks so fast I only get about twenty percent of the words. It can be like listening to a foreign language that one's only just learning.