Technically speaking, the shields wouldn't have to destroy a ship by compressing it just to destroy it. If the shields move in toward each other to crush a ship, they could just as easily target the masts below deck. I can only assume that it would act in the same fashion as if a cannon ball had been launched through the front of the ship to the back of the ship, which would break the masts, causing the ship to capsize within moments, since the load-bearing pillars would now be gone leaving the ship nothing to keep itself sturdy and together.
but then it would only affect larger ships, and not small ships, since the shields can't be within 5 feet of each other, typically masts on smaller ships are more thin.
