If you are seriously expecting problems, I would agree that a metal hull
and/or watertight compartment(s) is the way to go.
For the rest of us, we either have to stop the leak or pump water
out faster. Years ago, I considered and followed all the well intended advise about big pumps and schemes to pump water out by diverting the engine
pump, the fresh water pump and you name it.
Then I saw some data on the amount of water even a 1" hole would let into the boat and I came to the conclusion that I'd never be able to pump water out that fast. The inflow is unbelievable. That was confirmed last summer when I was was part of a salvage
crew trying to refloat a partially sunken barge--six
2" gas driven pumps couldn't keep water out faster than seemingly minor leaks
were letting it in. Just look at the water that comes in when you swap out your speedometer sensor impeller. So I am now of the opinion that if you breach the hull
in any way large or small, the only option is to do something to stem the flow of incoming water ASAP.
plan is an assortment of ways to slow the water coming in from the outside like collision
mats, etc. Then another assortment of inside the hull fixes to further slow the water and finally "hydraulic concrete" which sets fairly quickly underwater (Home Depot). The bilge pump
is just to evacuate the considerable trickle that is left over.
If you look at all the places such a hole could occur like inside lockers and hard to reach places, they all have their own best fixes. You have to be creative. Look around the boat and ask yourself how you would plug
holes in different areas. If it is a confined space, maybe inflating a beach ball or air matress in the locker will buy you time. I've seen $1 foam swiming pool floatation "noodles" ripped apart and stuffed in small cracks to good effect. One thing alone is not going to fix it. You have to progressively slow the leak until you can execute a semi-permanate fix like filling the compartment with concrete or something. BTW--the expanding foam in cans does not work. It will float away and stick to you--I've already seen this tried.