If you were interested in directly observing life below the water's surface, you would have a few options from which to choose to accomplish this objective.
Snorkeling is one option.
Snorkeling does not require extensive training and most people have enough basic skills to master this technique rather easily. However, your movement is restricted to the surface of the water, precluding direct contact with aquatic life beyond arm's reach. Your perceptions are limited to visual observations that may result in incomplete information about habitat, food sources or swimming patterns of aquatic life. With this technique, you are able to gain a deeper appreciation for life underwater through exploration deep below the surface. Additional information about aquatic life is accessible to the scuba diver.