Not P but Moby-Dick (46)

[Mike Jing]

>From Chapter 57:

Then, again, in mountainous countries where the traveller is continually
girdled by amphitheatrical heights; here and there from some lucky point of
view you will catch passing glimpses of the profiles of whales defined
along the undulating ridges. But you must be a thorough whaleman, to see
these sights;

What does "thorough" in "a thorough whaleman" mean here?

a. Chiefly in predicative use. That carries out or promotes something
thoroughly; taking pains to do something carefully and completely.

b. attributive. Chiefly British. That is fully the kind of person indicated
by the noun; absolute, complete, out-and-out.

All the existing translations I have at hand chose b., but a. seems to make
more sense to me.