Terrestrial organisms spend most of their life on land. One of the most important adaptations to live on land is the presence of limbs that allows the animal to walk on land. An example of organism with this adaptation is the lion, or a dog, or any other mammals with four limbs to walk on land.
In opposition to that, organisms that lives on aquatic biomes would not benefit from having the same limbs, as they need to swim instead of walk. So, one adaptation that aquatic organisms have is physical characteristics that allows them to swim, such as flippers. Therefore, examples of organisms with this adaptation are fishes, whales and dolphins (they all present flippers to get around on water).