It's a day out! Duggee and the Squirrels are off on an underwater adventure with Betty's dad in his submarine. They see all the wonders of the underwater world, including a giant sea stallion and some jazz fish. And to the Squirrels, all those coloured buttons that work the submarine are just as interesting as what is outside. Betty's dad has a tricky time amusing the Squirrels. Thank goodness for the school of fish!