The **submarine effect** occurs when, in an accident, the body of the driver or passenger slides downward, beneath the seatbelt. This happens because the seat is reclined backward and the seatbelt is not properly positioned or adjusted. To avoid this effect, it is important to:

- **Fasten the seatbelt properly** and ensure it is well adjusted to the body.
- **Do not place objects** like towels, cushions, or covers on the seat, as they can cause the body to slip.
- Maintain a **proper posture** while driving, avoiding reclining the seat too far back.


These measures help ensure that the seatbelt functions correctly and prevents the body from sliding, thus protecting the vehicle's occupants in the event of an accident.