actually the church referred to as the mariners church is no longer in existance.it was known also as trinity church.
i discovered this when looking for marriage cert.
the good news is that a lot of church records remain and are on microfilm at the public records office in belfast.
they have a good website ,and any search engine will get you there.
trinity church[mariners] was off corporation street very close to the seamens church described.i think it was a presbyterian church.one of the last ,if not the last,ministers was henry brownrigg.i believe it was turned into a meeting hall around 1920.
hope this is of help.
i have a picture of it if you care to e mail me