It is two person water bike.
Four bar linkage (yellow left pedal, green conrod and pink crankshaft) is used to convert pedal oscillation into rotation of propeller like in foot powered sewing machines.
Turn the pink wheel clockwise a little at starting going forward if the linkage is in its dead position.
Blue handlebar is for controlling the blue rudder.
Two yellow pedals are connected together by violet conrod creating a parallelogram mechanism.