That means the hull remains solid and intact and no water comes into the hull or hulls or the opposite of catastrophic hull failure. Properly designed boats are more than capable of slamming into the bottom or other hazard in the water without sinking. See the video of the 5800 hundred and all the boats with scratches on the keels in any BVI anchorage. The good ones just get scratch when they slam into the bottom under power or sail.