Some fish that cannot swim against the current avoid it by staying close to the bottom and behind rocks, like darters and sculpins. Others, among them bluegills and other sunfish, congregate in the slow-moving waters under trees and at the inside of bends in the river. Students will infer the relationship between streamlining in air and in water. Finally, students will interpret reasons for different fish shapes in varied aquatic environments, and understand that animals and their natural habitats are well matched to each other. Wait for the water to settle down.
Water is much more dense than air.
This means that even slight differences in shape can cause a difference in drag. If a fish is less streamlined, it will take more energy to swim. Air is much less dense than water, so the force needed to move through air is lower. This means that land animals can have lots of different shapes. Even so, streamlined land animals move the fastest like the jaguar.