This is a classic toy from the 1950s (given away free in cereal boxes) that you don't see around much anymore.
I remember my dad getting me one when I was a boy in the 1980s, but haven't really seen them around since.
After doing some research, here is a really good comprehensive website dedicated to them:http://torgo.org/bpsubs/
On this website it states that there is no 'clear answer' as to how to make your own baking soda submarine. Well, now with 3d printing technology, the answer is simple - model and print it!
Date Made: June 2013
Approx Cost: (Cost of printing?)
Approx Time: 3 hours modelling (plus printing time)
(Note: image taken from http://jamesrising.com/2011/04/23/what-wine-goes-with-fruit-loops/ under fair usage)