Hello, budding biologists! Let's dive deep into the world of aquatic habitats. There's a lot to learn about the physical properties of water and how it impacts the lives of our aquatic friends. Ready? Let's go!

Think about when you're swimming. Why don't you just sink to the bottom? It's thanks to a super cool thing called buoyancy. When something is in a fluid (like water), the fluid pushes up on it. If this force is stronger than gravity, you float! If not, you sink (sorry, heavy rocks!). This is all about density: objects less dense than water float, denser objects sink.

This is great for aquatic animals. Their bodies are about the same density as water, which means they don't have to use much energy to stay afloat. Fish even have an air-filled swim bladder to control their density! Isn't that neat?

Just remember: air doesn't give much buoyancy, so animals like birds have to work harder to stay aloft.

Ever try running in a pool? It's much harder than running on land because water is "stickier" than air. This "stickiness" is what we call viscosity. The higher the viscosity, the greater the friction and resistance to flow.

Sea creatures feel this too. Imagine them like they're always moving in slow-mo! Plus, the viscosity of seawater is even higher than freshwater, thanks to all those dissolved salts. Water's viscosity is about 50 times greater than air's at the same temperature. So it's much easier for a bird to fly through the air than a fish to swim in water!