An estimate of over 2-million aquatic species dwell in our oceans. And while it is easier to see seals, walruses, and sea lions hauled on rocks or beaches to sun themselves, most others aquatic dwellers will take a little more effort. Fortunately, many areas offer whale-watching excursions so we can go into their living room to witness their splendor. While there are only 120+ species of marine mammals, the waterways are populated with a acountless number of plants and fish species, too.