I am so excited! I just read about this word this very day at lunch, while I was reading through a 25-year-old book on Canadian English. I'd never heard it before. Here's what my book had to say:

gunk hole - (marked in the Dictionary of Canadianisms as a localism) 'tiny cove with deep water right to the shore'; thus to gunk-hole is to move from one such cove to another, fishing and idling.

Talk about serendipity!

(From Our Own Voice: Canadian English and how it came to be, R. E. McConnell, Gage Publishing Limited, Toronto, 1978.)