Can a submarine lay mines directly ahead of a convoy?

Could a submarine quickly lay a string of mines in front of an approaching convoy?

Yes, given enough distance, but zigzagging may bypass the field; confined routes and straits offer better placement and a greater chance of multiple hits.

A submarine with enough lead time could release a line of mines ahead of approaching ships. The difficulty is predicting a convoy that zigzags: a course alteration may carry every ship around the field. Straits and other confined passages are better mining locations because traffic is more likely to hold a predictable course and potentially strike more than one mine. Multiple strikes offer a much better chance of sinking a target, so geography and traffic predictability matter as much as the submarine's ability to dispense mines quickly.