A Boston man recently saw a sunfish in Boston Harbor; his reaction, including misidentifying it about six times, is hilarious. The video at the linked page has positively Deadwood-level NSFW language, so I’m going to spoiler it.
It’s about 5 min too long, IMHO. Not sure why he was so convinced it was sick/dying, but nice he was moved to try and help. Sort of.
Here’s a resource to find a marine animal rescue organization in the US: http://www.nmfs.noaa.gov/pr/health/report.htm
Sunfish are pretty weird though, when I first saw one I was pretty much the same (minus the swearing and the Bostonian accent).
I love how casually you mention having seen one in person. “First time” indeed.
(Sunfish ARE weird, though.)
What, they look pretty normal to me! 
I first saw a real half-fish ocean one in the wild when I was on a boat for some reason in San Diego. They like flirting with people. Also a dead one.
I had to stop watching when they called the Coast Guard. Because I was laughing so hard I needed my inhaler.
This has the makings of the next internet meme. Credulous Man: “Holy shit, Jay! What the fuck is that, Jay?! Is that a fucking shoe, Jay? - A fucking SHOE! Am I lying?!”
They thought it was sick/dying because sunfish just sort of float or cruise slowly at the surface, on their side. Which is pretty unusual behavior for any other fish.
The first time I saw one we circled it a few times too, just to figure out what the hell it was.
I miss Boston, sigh.
As a former Bostonian, I found that hilarious. Extra props to digg.com for the great headline: “Extremely Boston Man Can’t Comprehend A Sunfish”.
When we visit the Monterey Bay Aquarium, one of my favorite things to do is go to the big tank and watch the sunfish swim around very…slowly…
So… what did they do with it?
They said they tried to bring it on board the boat but couldn’t, so they just let it go. They’ve been all over local radio the past few days.