If the submarine continues on its present course until a depth of 200 meter, how far will it have?

The answer depends on at what angle it is descending and how deep it is already. Assuming it is at the surface. If it is not descending (i.e.the angle is 0 from horizontal) it will never reach a depth 200 meters. On the other hand if it is descending straight down (i.e. the angle is 90 degrees from horizontal) it will travel 200 meters. All distances in between are possible.