Eli5: How does water not get inside ships or submarines through the motor shaft?

Question

Eli5: How does water not get inside ships or submarines through the motor shaft?

In: 112

Answer 1

In most cases it does leak a little bit.

Boats have pumps called bilge pumps that pup out the water from the lowest points of the boat. Its not unusual for the shafts to leak a little bit. When they leak a lot, they need repair.