Your sentence is mostly clear and correct! Here is the original sentence:
"The beaver builds its home from sticks and clay. The lodge is safe in the water, and beavers dive underwater to get inside."
Some small improvements can make it even clearer:
- Change "The lodge is safe in the water" to "The lodge is safe because it is in the water." This explains why it's safe.
- Alternatively, "The lodge is safe in the water" is fine if you're keeping it simple.
So a corrected version could be:
"The beaver builds its home from sticks and clay. The lodge is safe because it is in the water, and beavers dive underwater to get inside."
This sentence is clear, grammatically correct, and easy to understand for a 7-year-old.