Fascinating stuff all this, I was reading up on some of the world war 2 things they used to do such as counter flooding and dumping heavy fuel oil into the sea around the vessel to increase buoyancy. During the times of wooden ships they used to hang heavy tarps over the side with multiple ropes stitched on to seal holes, shame they cannot come up with a similar BDR scheme using a metal shutter type device that can be lowered over the side allowing suction and water pressure to do the work.
Tomorrows World ( remember that ) showed some fascinating things, one for small boats was a rubber umbrella that you would push through the hole and then open, the water flow would push it against the hole sealing it. Often wondered if it ever went into production, similar to the chaff distress flare they showed.