This is a special kind of transport, Sometimes used in an emergency, As they're able to fly and hover, And help rescue people lost at sea.
A Helicopter
15
Susy is traveling by ship from south of the equator to the north. She is in a cabin with a bathroom, but no window. Sally has no compass nor other instruments. Yet, without leaving her room , Susy will know when she's cross the equator. How
The bathroom drain will change direction once she crossed the equator.