Looking back, the Sunfish (Mola Mola) may very well have been what I hooked at the time. I remember now that we saw at least 2 huge ones that day just floating in the surface like they were dead. At the time nobody knew much about them but the skipper mentioned that they weren't dead but they "just floated around like that". He said he'd seen a fair number of them that year. The ones I saw were easily over 100+ lbs. At the time I never considered them to be a possibility because I was under the false impression that they did not swim at greater depths. I found a neat website with more info and some video on them. Although they seem to feed on jellyfish, I can see how when they are swimming upright it would be easy to accidentally snag one on their elongated dorsal.

Here is the website:

http://www.oceanlight.com/html/mola_mola.html

I guess these guys can get up to 3000lbs. No wonder the skipper wasn't waiting around.