On a certificate showing the marriage between Alexander Hannay and Elizabeth Manners dated 25 Aug 1811 both are from the same parish which is decreed to be Liverpool Mariner. Does anyone have any info about this please?

My gr x 3 grandfather was son of this couple [I think] born 1st Aug 1811 but not bapt til 30 Sept 1811 and the baptism was at St Peters Church Liverpool.

Is Liverpool Mariner a church? and is St Peters anywhere near?
If anyone knows Liverpool well - any help is appreciated.
Thanks
Viv