It's been way too long since I watched Raiders, but I remember it being great so I'll have to watch it again.
That definitely sounds stupid. The only saving grace might be that U-boats, unlike modern submarines, very rarely went underwater. They had diesel engines that ran the engines on the surface and also charged batteries. They could use the batteries underwater, but they didn't last long. When they attacked they'd go underwater so they could ambush the ships they were attacking. But, to set up for that attack they'd race ahead of the ship while staying above the water, then go under for the ambush. Even a lot of the attacking happened above the water. Yes, they had torpedoes, but they also had deck guns. Since their targets were mostly commercial ships, they didn't have to worry about the ships shooting back.
On the other hand, the fact they were used on the surface meant that there was almost always a crew on the conning tower. Technically you could do everything without using the conning tower bridge. But, they almost never did. Even during storms they were up on the conning tower, not sheltering inside. It was awful being exposed to the elements like that, but the visibility through a periscope was awful compared to standing outside.