In my world, there is a race of intelligent protists ( designed by a race of highly advanced aliens ) whose entire population is located in a little lake about the size of a football field ( they themselves are 75 - 100 μm ). In terms of technological development, they have reached the bronze ( ish) age , with the capability to produce limited electric currents to extract dissolved metals from the water. Due to them being both protist and intelligent and microscopic, they know quite a bit about chemicals , and since their discovery that there is something beyond the waters edge, they have found various ways to produce / capture the elusive, super buoyant material known as air, and use it to conduct experiments on how chemicals may react when above the waters edge.
The Essential Question : what would it take to produce such a land faring vessel?
Edit: the eyesight of the protists is roughly equal to that of humans