When the "off the hook" term is used these days, it's to make something sound awesome.
It's awesome for the fish that got away...
I can see him now... "Dude! you ain't gonna believe it! damned ole fisherman had me hooked. He was reeling me in. I thought I was gonna be pan-fried by nightfall. But I managed to get loose. I got away! It was off the hook!"