A vehicle includes an engine compartment and two rockers fixed relative to the engine compartment. The two rockers define a passenger cabin. A first water sensor is disposed in the engine compartment, and second and third water sensors are disposed in the passenger cabin at the rockers. A seatbelt buckle is disposed in the passenger cabin and has an actuator. A control module is in communication with the water sensors and the actuator. The control module is programmed to actuate the actuator based on signals from the water sensors.