Glasgow and Dublin are 247 miles apart.
There are no ferries between Manchester and Glasgow. Drive or take a train.
From Holyhead to Dublin (Dún Laoghaire):Stena Line: 3h 15min (Stena HSS)From Holyhead to Dublin (Dublin Port):Irish Ferries: 1h 55min (Dublin Swift)Irish Ferries: 3h 15min (Cruise Ferry)Stena Line: 1h 55min (Superferry)
Yes. There are lots of ferries going from Holyhead in north Wales to Dublin port and to the port of Dún Laoghaire in the south of Dublin.
There are a variety of times when ferries from Irish Ferries depart and arrive. Some of the times that the Dublin Swift Fast Ferry departs is 11:50 and 17:50.
Lisbon
Glasgow has 635,000 in the city and 1.7 million metro Dublin has 554,000 in city and 1.4 million metro
About 230 miles / 370km
There is no direct train journey from Dublin to Glasgow. There are a wide variety of ways you can make part of the journey by train. You could get a train to Belfast and then a ferry from Larne to Stranraer, and then a train to Glasgow. You can fly from Dublin to Prestwick, and get a train from there to Glasgow. You can get a ferry from Dublin to Liverpool and travel by rail to Glasgow that way. As there are many different options, then there is no single answer to your question.
Bristol is nearer to Dublin. There are no standard ferries operating between the two. You would need to go to the town of Holyhead in Wales to get a direct ferry to Dublin, or go to Fishguard and get a ferry to Ireland and then drive to Dublin.
Fishguard is in Wales, not Ireland. You'll need to take a ferry to get from Fishguard to Dublin or Vice Versa. There are daily ferries, they take a few hours.
About 40 to 50 minutes.