Complex sentence: Frogs also create vortices that shed off their feet when swimming in water; the vortices from the two feet do not interfere with each other; therefore, each foot is generating forward propulsion independently.
Split into simpler sentences: Frogs also create vortices that shed off their feet when swimming in water. The vortices from the two feet do not interfere with each other; therefore, each foot is generating forward propulsion independently.