Uther Pen Son of Nethawc/Nechtan and Manannan Son of Lir: Is This the Link to the Arthur Birth Story?

Statue of Manannan Mac Lir

Pretty much anyone who has studied the Arthurian birth story knows that it was copied from one of two sources - or perhaps from both of these.  The first is the Irish tale of the conception of Mongan, while the second is the birth of Herakles.  

For those unfamiliar with the Irish version, I kindly refer you to these translations:

https://www.maryjones.us/ctexts/mongan2.html

https://www.maryjones.us/ctexts/mongan.html#birth

Now, the real question concerning possible incorporation of the Mongan birth tale into that of Arthur is whether this came about because Uther was identified with Manannan the sea god or merely because we know Mongan was later killed by Arthur of Dyfed (Bicoir in the Irish Annals is merely a corruption of Petuir, i.e. Pedr).  

I have made a big deal about a possible Nechtan father for Uther.  Most recently, I revisited the idea here:

https://mistshadows.blogspot.com/2022/07/was-i-on-right-track-with-uther-pen-son.html

The possible significance of a Nechtan father for Uther naturally leads to any number of such personages, from Pictish or Scottish Lowland figures to St. Nechtan at Tintagel:

https://mistshadows.blogspot.com/2019/05/uther-pen-son-of-nethawcnwython.html

Nechtan is the Celtic cognate of Classical Latin Neptune, the sea god.  And from what we know of the Nechtans, including a god of that name in Ireland, they were generally associated with water.  The Lir made father of Manannan in Irish tradition is simply the word for 'Sea'.  We could thus do the following, which seems to show a synonymous meaning for the patronymics involved:

Uther Pen Son of Nethawc/Nechtan

Manannan son of Lir 

Whether this can be used to help substantiate an identificaiton of Uther Pen of the MARWNAT VTHYR PEN and the Penn son of Nethawc of CULHWCH AC OLWEN is debatable.  But I think it must be allowed to stand as a valid argument in support of the notion.