There is no way to reach Noordpolderzijl directly by public transport.... it's located at the end of the world, unknown by the masses.

By train>taxi
From Groningen CS you can take a train to Warffum, then call a taxi (see below) for a short drive to Noordpolderzijl (6 kms).

By car
from Groningen ring > N361/N363 to Winsum/Uithuizen. In Warffum centre village go to the left > Noordpolderzijl.