The submarining effect occurs when a child slips under the harness or seat belt, which can cause the pelvic strap of the harness or belt to press on the soft parts of the child’s abdomen, with the consequent risk of injury.
This submarining effect is normally produced either by the incorrect adjustment of the seat belt (for example when, despite the need for a booster seat or cushion, the child travels directly on the vehicle seat using the adult seat) or when traveling with excessive slack in the harness or belt. To avoid this submarining effect as much as possible, it is important, as mentioned above, to avoid any slack and to ensure that the child sits as close as possible to the back of the seat.