The bigger the fish like that one, the faster they seem to die during the fight. Not sure why that is. Oxygen depletion, maybe. About all you can do at that point is use the boat to plane the fish back up to the surface a little bit at a time. Bump the boat forward a little bit, reel, then repeat 999 times.
Did she catch it on a Zebco 33? now THAT would be impressive...
I would imagine that the geriatric nature of the fish might also be a factor in the bigger/older ones like that croaking on the line. To get that big, a fish has to have a blazing metabolism early in life.
Live fast, grow huge, die young... Marlin and Dorado are the James Dean's of the fish world.