Which concept explains the fact that many forms of aquatic animals look alike even though they have very diverse ancestors?

The concept of convergent evolution explains the fact that many forms of aquatic animals look alike even though they have very diverse ancestors. Convergent evolution occurs when different species independently evolve similar traits in response to similar environmental pressures. In the case of aquatic animals, the need to swim efficiently in water has led to the evolution of similar body shapes and structures in diverse groups of animals, such as fish, dolphins, and penguins.