Final answer:
In a water landing, exit the aircraft after it has stopped completely and the flight crew instructs you to do so, illustrated by the Gimli Glider incident where all passengers were safely evacuated after the aircraft landed without power.
Step-by-step explanation:
In a water landing scenario, you would exit the aircraft only after it has stopped completely and you have been instructed to do so by the flight crew. In the historical case of the Gimli Glider, where a Boeing 767, piloted by Captain Robert Pearson and First Officer Maurice Quintal, lost all power mid-flight due to a fuel miscalculation, the aircraft was safely landed on a decommissioned runway. Despite the lack of power, the pilots glided the plane to safety and passengers were able to exit the aircraft after an unpowered, but safe, landing with buckled landing gear.
When discussing dynamics in physics, for example, an object in free fall without air resistance or the deceleration of a plane as it lands, the principle is that an object continues in its state of motion unless acted upon by an external force. Thus, for the safety of passengers during any emergency landing, they must remain onboard until the airplane has come to a complete stop and they are directed by the flight crew to evacuate.