If you are going to meet in one of the indoor car parks, i would suggest making it by one of the three main points.
Those who don't know, Blue water is in the shape of a triangle with a department store at each point, John Lewis, M&S and House of Fraiser.
The car park is arranged between these points so it will be easier to pick one of those department stores and meet there.
For instance, by the John lewis entrance in the car park between there and house of fraiser.
This may help explain.
http://www.bluewater...s/where-to-park
Just bare in mind that they close at 10PM so don't meet too late!
Ben