Question

Explain the movement in bird
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Answer 1

Density is a measure of an object's mass in comparison to its volume. Water has a much higher density than air which means that animals must push back against the water in order to propel themselves. This is why water animals often have paddle-like fins that are efficient at pushing against the dense water. This is also why a streamlined shape is beneficial as it can cut through the water like a torpedo.

2) Buoyancy: It might seem strange to think that fish need to actively work to keep from sinking, but gravity applies to them too. Buoyancy is the ability to stay afloat, and it is all a matter of density. In simple terms, things with a higher density than water will sink, things with a lower density than water will float.