There aren't too many things involved and if you take things apart a lot like me, you should have most of these things. I will also attach Radioshack links next to the parts that they may carry.
(3) Push buttons or switches http://www.radioshack.com/product/index.jsp?productId=2062495
(3) DC Motors (at least two have to be the same) http://www.radioshack.com/product/index.jsp?productId=2102822
(?) I built my frame out of pieces from a physics workshop kit, but as long as it holds the motors and isn't too heavy, anything should work
(1) 9V battery connector, or if your using different voltages, a different battery holder. http://www.radioshack.com/product/index.jsp?productId=2062218
(4) Empty Film Canisters. These will hold the air that will float the ROV (Remote Operated Vehicle) back to surface.
(3) Propellers. These go on the motors to propel the ROV. I found one off an old model plane and two laying around.
(1) Some solder. Most anything should work. http://www.radioshack.com/product/index.jsp?productId=4314832&filterName=Type&filterValue=Solder
(1) Some hot glue.
Soldering Iron. anything should do. Just needed to solder a few pieces together. Make sure you have permission to use this.
Hot Glue Gun. I used this to glue to film canisters and the motors onto the frame.
Helping Hands. These work REALLY good. I used kind of a make do one, but these help when your trying to solder something.
A Bath Tub. Something to test it in.
(Optional) Wire Strippers