The C Dory hull is relitatively puncture resistant because of the balsa core. The outer layer is fairly thick, and penetration is avoided because of the shock absorbing quality of the balsa. Plus the balsa and inner glass liner prevent breaching of the hull.
Bilge pumps are a bit over rated. If I really wanted to move water I would use a gasoline powered 3" trash pump, or a diaphragm pump. We carried a double diaphram Whale pump on our long distance boats--a bit big for a C Dory, but it would move water, resist plugging (a common failing of the centrifical pumps).
I keep a 3700 Rule as a "rescue pump" on my boat with battery clips for use on other boats, or mine in case of an emergency. The Rule type of pumps will do OK--but remember that they are rated at 13.7 volts (not 12)
They are rated with smooth tubing and no head pressure:
see:
http://www.powerboat-reports.com/sample/bilge.html read the last several links on testing of various pumps.
We had occasion to use Splash Zone compound--when we hit an uncharted pinacle rock off Turkey. There was a fair amount of splintering of glass on the bottom of the keel (over 1.5" thick however so no danger).
That night I hand sanded (wet and dry #36 paper) and then preped enough Splash Zone two part epoxy to cover the area. It was backed by wax paper, cardboard and then 1/4" ply. Spanish Windlass rope tension was put all of the around the boat to pull this material into place. The next morning it had set hard, and 6 months later when I hauled the boat and ground out the damaged area, it was evident that the Splash Zone compound had worked into the crevices and was well adhered. The area was reglassed.
I have also see a number of hurricane damaged boats with large holes--from other boats or pilings, where plywood was roped in place, and then "Great Stuff" foam (which sets up under water) was sprayed in place. If you have ever worked with this, you know that it is very stickey, will expand and adhere well to almost any surface. Several spray cans will do wonders in saving a boat.
Duct tape is variable--sometimes it works very well--other times it is hard to get good adherence. But it is worth carrying. I am not sure how many nerf balls, or soft wood plugs to carry (but I have never had to use one)--thru hulls should have working sea cocks.
All in all the C Dory is a very safe boat and difficult to sink. Most of our voyages are within 100 miles of land, and rescue is usually quick if necessary. Trying to patch a boat in a seaway is not easy, and this is complicated if the water is cold, the seas are rough etc.
I once bought a boat very cheaply, because it kept sinking. I found the small hole in the centerboard trunk--which previous owners had missed. The repair was with epoxy from inside. I had to put in an epoxy, and then back it with wax paper, cut blocks and wedges to hold in place until the epoxy cured. I have worked with the solid bars of epoxy, where they are cut and then worked to catalize them. They may work in some situations, but I would have something like Splash Zone compound as a back up where you cannot get that to adhere or fill the void.
Years ago, when the Coast Guard was primarly a rescue agency, I watched a beautiful 55 foot ChrisCraft driven on a reef at Catalina. (Car dealer's son was driving)--and it tore the bottom, shafts, and rudders out of the boat. We pulled it into shoal water, and got two big logs under her chines before the Coast Guard arrived. The CG crew had plywood, some ring nails / screws, caulking compound and was able to cover the holes in the bottom of the boat, to the point where their pumps were able to keep up with the water inflow and towed her back to Redondo Beach.
