Grammar check for a 6-year-old: sentence about a ray swimming like it flies

Correct, simple sentence: A ray swims like it's flying, flapping its fins like wings.

Another correct (a bit more formal) version: A ray swims as if it were flying, flapping its fins like wings.

1. Start with a capital letter. Sentences begin with a capital: 'A' instead of 'a'.
2. End with a period. Put a '.' at the end of the sentence so it is complete.
3. Say it the natural way. 'As if it were flying' or 'like it's flying' sounds better than 'as if it flies' when you imagine something.
4. Use the comma correctly. The comma before 'flapping its fins like wings' is fine because that part explains how the ray swims.

Very short versions for practice:

A ray swims like it's flying. It flaps its fins like wings.