Very heavy seas. What are my options?

I'm nearing the end of my second patrol in U-53 (gwx 3), heading south down the East Coast of Britain. There's a huge storm outside and very heavy seas. I know the North Sea can be rough, but the waves are over the conning tower. I'm trying to play realistically, so I submerged to get out of the weather and spare my watch crew. The problem is, even after spending quite some time submerged, the weather hasn't let up. I've kept my speed to one-third to conserve battery, but I'm down to 25% none the less. I don't think that a U-boat would have been able to keep a watch crew on the bridge in this kind of weather, but I also can't stay submerged forever either. I know that my crew wont get blown overboard in the game, but if this were real life, what would my options be?