Yes, it is possible to hang out in a strait submerged, and so long as it is a choke point in a shipping lane, you will find targets. The problem is that you're submerged, burning up your batteries and you'll need those batteries when you get in combat with an escorted target. So you are crippling your ability to fight.
Then when you surface, you have to stay surfaced for very long amounts of time to recharge. Your risk of being spotted is about the same as if you stayed on the surface and just submerged when forced to. But you are not ready to fight because your batteries are always below full charge. There's no peace like knowing you can hit the jets at ahead emergency for 30 minutes and not worry about your battery! It'll save your tail!
