Short answer (corrected): An island is like a boat made of land. Water goes all around it.
Another simple way to say it: An island is a piece of land surrounded by water.
Why this is better (in easy words):
- "Land-boat" is not a usual word. Saying "boat made of land" or "piece of land surrounded by water" is clearer.
- Adding "it" at the end ("around it") sounds natural, but you can also say just "around" and people will understand.
- Both corrected sentences are short and easy to say out loud.
Try this game: Point to a picture of an island and say one of the corrected sentences. Which one do you like best?