De or het zeehavenpolitie?

The correct Dutch article is:

de zeehavenpolitie

Rule Words ending in -tie and -sie: almost always de. See the rule

How to use zeehavenpolitie

the zeehavenpolitiede zeehavenpolitie
this zeehavenpolitiedeze zeehavenpolitie
that zeehavenpolitiedie zeehavenpolitie
our zeehavenpolitieonze zeehavenpolitie
your zeehavenpolitiejouw zeehavenpolitie
every zeehavenpolitieelke zeehavenpolitie
which zeehavenpolitie?welke zeehavenpolitie?
a big zeehavenpolitie / the big zeehavenpolitieeen grote zeehavenpolitie, de grote zeehavenpolitie