The Diving Sub by Toysmith is an old fashioned toy that was a cereal premium in the 1950's!

Ages: 4

But it still dives over and over again for hours of fun. Pull the top 'radar assembly' from the sub and dampen it in a container of six or seven inches of water. Fill the bubble chamber with household baking powder, not included. Insert the 'radar assembly' and shake vigorously and the sub will submerge and surface automatically!