The Demon Of Scattery. For a start, dig this sunset or sunrise photo of Hog Island (p. 147) on the horizon.
"Dreaming" and sailors seeing a sea serpent are two strong parallels between Poul Anderson and Neil Gaiman. But they are just parallels. In particular, the two authors make different fictional uses of dreams. Nevertheless, the sheer number of the parallels is quite entertaining.
Mananaan tells Skafloc:
"'Kindred of yours were caught in it, and at the end even I played a part.'" (p. 9)
I have not located Skafloc's kindred yet but Brigit, the former nun, thinks:
"...it is not [Skafloc's] Thor who rules this storm. Mananaan Mac Lir is rising now in wrath." (p. 141)
Thus, Mananaan narrates Brigit thinking about Mananaan. Read on.