Off the top of my head I can think of a couple of examples of mates going ashore and getting a law degree. Both very successful.
From the many sad tales of failures (meaning having to go back to sea and not liking it) I’ve heard many if not most involve such things as mariners trying sales related fields such as real estate or financial type services.
A few have muddled through but to me it seems getting some further academic credentials or at least training of some kind is a big benefit.