If your find your having trouble setting up a waterstrike table in Template Studio, please see below.
Once you open the example go to "Table Columns" from the ribbon, there you will see the columns and how they are setup.
The way its setup is that it uses, firstly the "Water Strike - General" table to bring that data back for columns;
The "Time Elapsed" and the "Rose to" columns are pulled through from the "Water Strike - Details" table using expressions. These are;
fixed(numberordefault(max([Aggregate.WaterStrikeDetails.TimeElapsed]), 0), 0, false)
fixed(numberordefault(min([Aggregate.WaterStrikeDetails.DepthWaterValue]), 0), 2, false)