describe the method by which Santiago catches the marlin.

Santiago just "plays" the marlin - lets the marlin swim along for awhile and then gradually pulls him in a little bit at a time. The plan is to wear the marlin out and be patient with his strength and "stick-t0-itive-ness." Both are stubborn to the end.

He uses bait and a line..... an enormous amount of sweat and energy, and the things he's learned through experience to hook the fish.