Any boat that runs inlets or spends time on open ocean should be prepared to handle getting pooped, slammed, broadsided, or whatever else causes a flooded cockpit.
More than adequate drains are only the beginning.
Just for fun, calculate the weight of your cockpit full of water, than add that number to your boats normal loading and then the new waterline you will be sporting. All the scuppers in the world do no good when they are underwater, and flappers are pretty useless when submerged.
The housekeeping in the cockpit must be immaculate, because everything loose will immediately move to the drains.
Chair cushions, rugs, sponges, rags, chamios, fishing gear, fish, food, beer/sodas, Ice, towels, t shirts, etc will plug them up.
Many boats have unsealed hatches that will float, so these guys need to have huge bilge pumping capability.
Your best friend in such an emergency is the 5 gallon bucket (not the old one that has sat out in the sun for years), and strong arms that can bail like hell for a sustained period.
If it happens to you, get on the throttle, and do not stop!
Don't ask me how I know!