I have often thought that coffee smells fishy sometimes, as in literally like fish, particularly canned tuna (one of the few foods I have always and truly hated, largely due to the smell). I like the smell of coffee, and it's never an overwhelming fishy smell (like when my mom, despite my brother's and my howls, would make tuna casserole), just a faint whiff in there with the regular coffee aromas. I first noticed it on someone's coffee breath, and afterwards from time to time in coffee itself, usually the beans or ground coffee, not the brewed liquid.
I was just setting up the coffee for tomorrow and got that old fishy whiff, and it occurred to me that there is probably some chemical or molecule common to both coffee beans and fish (or at least canned fish). One of the things that 2+ years of perfume connoisseurship has taught me is to always trust my nose! Many of the smells I used to think I was hallucinating or imagining are right there in nature (or non-nature, as the case may be); common "ingredients" can often be confirmed with a web search. At the very least, you can find other crazy people like you who think single-malt scotch smells like Band-Aids, for example. Sure enough, I'm not the only one who thinks coffee (especially darker roasts) smells like fish. Here's a thread with some theories on the coffee-fish connection; could be the presence of Ethylmethylamine (which has a "strong ammoniacal and fishy odor").
Other weird smell/taste connections: cantaloupe and acetone (nail polish remover); raspberry and clove (there's eugenol in raspberry, much as in rose).