While the ship is Anchored, it takes no damage. Cannons and portholes cannot be fired, sails cannot be opened, components on the ship such as storage boxes, ammo boxes, doors and hatches etc. take full damage, but the ships components themselves (anything that would cause it to sink) don't take damage.
Ships can only use Wooden doors, so using the ship as an immobile base wouldn't be viable due to it being easy to bust in to. Cannons can't be fired, so it won't be a case of having an invulnerable siege emplacement. It would literally be a sitting duck. An unsinkable sitting duck at that, but still a sitting duck.
