If the water was not deep enough at Southampton, would the passengers have to be ferried across, like Cherbourg and Queenstown?

[Cam Houseman]

Would that have delayed the departure?

 

[Ioannis Georgiou]

Would that have delayed the departure?

No, why should it?
This would have been not a "surprise" as Southampton was a very busy port.

 

[Cam Houseman]

I was thinking along the lines of, would ferries ferrying the passengers across the harbor take longer than her being at the deck, and Passengers just climbing aboard at the Gangway doors

 

[Tim Gerard]

It would take longer to get people on and off the ship if the harbor was too shallow to dock and they had to use tenders, but White Star Lines would know well in advance and the ship's schedule would have been set well in advance. I do wonder if they'd consider having the Titanic and Olympic sail out of Liverpool instead if the ships were too deep for Southampton.

 

[Ioannis Georgiou]

It's very likely they would have not moved to Southampton....
Aside from Adriatic the other big 4 (Baltic, Celtic & Cedric) sailed from Liverpool for several years.