Age of Sail naval combat very rarely resulted in one ship sinking the other.
This is for two obvious reasons:
A. Hunks of wood are very buoyant, and large crews can easily stop holes and pump out water. Cannonballs don't create holes much larger than their own diameter and can't shoot through water, so damage is limited to the hull at the waterline or above. Causing damage that threatens flooding relies on very specific conditions or deliberate action...
B. ...which combatants were unlikely to take, since the objective was almost always to capture, not destroy. This brings in the most prize money. In game terms, it is also far more fun, because we get to maybe seize a brand new vessel to play around with, rifle through its hold, etc.
And if we do get sinking ships, please don't make them blow up in a ball of fire when their HP reaches zero, like in POTBS.
Concrete wishlist:
Ships can take huge amounts of damage before sinking.
Ships receiving fire on the windward side when heeled can suffer shot-holes that cause flooding. This forces them to divert fighting manpower to the pumps to stay afloat.
Ships that sink do so slowly and realistically.
Captured ships are sent away with prize crews.
But if ships don't often sink, how do we win battles? Won't human captains be opposed to surrender and often choose to fight to the death?
Yes, and at a certain point, the game must take the decision out of human hands to prevent the irrational and trolling behavior that would otherwise ruin the gameplay.
Once a ship suffers too many casualties, the crew will naturally run down into the hold or otherwise stop fighting from exhaustion, demoralization or plain attrition. In this case, the officers should either automatically surrender the ship, be considered disabled/killed, or the game should communicate to the opponent that a boarding action would now result in effortless victory.