Have you ever felt how easy it is to float in the sea, but it's so hard in a swimming pool?
The sea has a secret ingredient: SALT! 🧂
In this lesson you'll do experiments, push some arrows, and even make an egg float — let's find out how salt water lifts us up.
Tap Next to begin →
When something floats, it stays up on the water. When it sinks, it drops to the bottom.
Tap each object to guess what it does in plain water 👇
Discover all four to continue your splash!
Water always pushes up on anything inside it. We call this push upthrust.
Tap the orange ball to see the hidden push arrows.
⬆️ Upthrust pushes up vs ⬇️ Weight pulls down. If upthrust wins, you float!
Salt water is heavier and thicker than plain water (we say it is more dense). Denser water gives a bigger upthrust — so it lifts things better.
Drag the slider to pour salt into the glass and watch the egg rise!
Saltiness: plain water
Add salt and see what happens to the egg…
The Dead Sea (between Jordan and Israel) is SO salty that people can lie back and read a book while floating!
Tap a card to reveal a salty fact!
Some things sink in plain water but float in salty water, because the push is stronger. Make your prediction for each one!
Will it float in very salty water? Tap your answer.
Salt water helps light things float — but a very heavy rock is still too heavy!
Here's the big idea you learned:
Next time you swim in the sea, you'll know exactly why the water lifts you up. Great work, scientist! 👏