Moin, moin! (greeting in Platt)

"Plattdeutsch" = German name for the language/dialect
"Low German" = English name for the language/language
"Platt" = short name of it

Contrast with "Hochdeutsch" = "High German" = what tends to be considered "standard" German.

Plattdeutsch is especially associated with Hamburg (called "Hamborg" in Plattdeutsch). So, "Hamborger Platt."

Hamburg is the seaport most associated with German shipping, so most of the sailor songs are in Plattdeutsch. If I remember correctly, only 1 or 2 of the "German" songs in Hugill's book are High German. The rest are Low German.

Plattdeutsch / Low German is slightly more similar to Dutch/Nederlands and English than High German.

Plattdeutsch pronunciation is different. For example, in Standard German the letter "S" makes Z sound of "Zebra." In Plattdeutsch, S makes S sound of "Seven." The orthography/spelling resembles Dutch. "R" has "rolled" sound.

Pronunciation of "Hamborg" is like /hamboich/.

I think some of the German shanty choirs "convert" the Plattdeutsch words/pronunciation to Standard German, so be careful when you listen to examples.

I think Hannes Wader sings with proper pronunciation.
https://youtu.be/gHtybtPxrEM

I am no expert on this. I'm just sharing what I learned after studying to sing the Plattdeutsch songs.