I picked up the one on a british sub, as it has some interesting facts with regard to this area of ops. but this could be on any sea.
- The currents around the islands were heavy, sometimes made it difficult to turn a sub, 'locking' it on it's course, even with full rudder.
- Thermal layers could prevent a sub from diving immediately, delaying the diving time in critical moments. They could also send the sub plummeting down nearly out of control, not to mention forcing the sub to bob up onto the surface ??
- They almost always used ship revs to estimate target speed. The hydrohone guy could identify the engine type and with revs, ship speed.
