WHOHAO 4 Pack Car Window Breaker and Seat Belt Cutter, Emergency Keychain Car Escape Tool with Glass Breaker Seatbelt Cutter,Car Safety Hammer,BlackUnderwater & Land Available Ordinary safety hammer cannot be used underwater due to water pressure. Our safety hammer adopts a knock collision strike design, which will generate huge explosive power to break the car window instantly. It can not only be used on land, but also easily break the window when underwater. You can use it to escape in seconds when cars falling into water. Escape in Seconds This window breaker adopts a knock collision design