The answers given are good. The air or gas pocket at the large end of the egg gets bigger as the egg ages-- that is why older eggs float to the top in a pan of water, and the fresher eggs sink down moree. As was said, a little bit of the top of the egg shell comes to the top of the water it is ok.
When hard boiling eggs-- it is best not to use the newest laid ones. They are harder to peel because NO air pocket has formed.