True. That is why the Germans had the quick-release sleeve/spacers shown in the photos above. When in combat, the ship slows down enough to keep the big guns free of water over the foredeck, and if the seas are so rough that waves wash over the foredeck anyways, then combat is simply not joined. Even with the blast bags used later, if sea water is sweeping over the foredeck and hitting the turrets, those big guns are unlikely to be firing at anything except in the most extreme emergency (the range finders get coated with salt water and thus ineffective, and the ship is moving up and down so much it becomes difficult to 'time' the shooting for targetting purposes anyways). Also, 'battle speed' for these ships was around 16-18 Kts, and flank speed was only 20-22 Kts at best, so it was not that big an issue in any case. Finally, cordite smoke within the turret during battle is at least as much a problem as a bit of seawater, and by leaving the gunport uncovered during battle, wind generated by the forward motion of the ship will help a lot in ventilation. As far as the big guns getting wet, it is important to remember that earlier battleships, particularly in the British Navy, but others as well often had main guns with no turrets at all ('open barbette' mounts), and the guns were pretty much completely exposed to the elements (and shellfire), as seen here:
And here you can see the problem......:
