You can catch a 600 lb fish on ultralight gear. Its a matter of setting the drag, how you use the poles tension, and how you remove the fish from the water after you have won, if you win.
That being said, catching even a large shark with an ultralight lessons your chances tremendously as one flick of the head or sudden burst of speed and its gone. We're talking requiring way faster reaction times and much longer reel times. Yet, Shark fishing with ultra-lights is a sport that people do.
Its all about fight, how long, and your odds. Decades ago, people used much heavier lines normally. Nothing says your drag has to be set at this level and sometimes hoss cating something in after you are wore out is the only way. It blows my mind how much fight is in a 60lb fish let alone a bigger one. Anyway, 30 lb is a good weight and about the most common that its strong but you don't give up so much spool. After all, you only have till the line runs out to turn them or its gone.
Which btw, if you do buy a open face, don't tie the line to the little knob on the reel. You can't turn that sucker, your options are only two say goodbye to your combo or go body surfing behind a big fish like a bad Moby Dick movie. I've seen my share of combos pulled right out of peoples hands.
Another little trick actually taught to me by the offshore folks that fish off oil platforms, when dealing with rocks, use your 30lb line but lighter leaders. Adjust your drag for the leader. That way if you snag and have to break it, it will most likely break at the leader and save your line.
You have to have patience to catch the big ones. Firs time you lay into one, you'll know it and it'll be a head rush even if you don't land him. Everything needs to be bigger and heavier. If surf fishing, you need the led weight from hell preferable with the prongs that sink into the sand and a bait so large the trash fish can't eat it. From shore, I prefer pier fishing or jetty but I've done my share of surf. We use to pull our van on the beach in TX, build a nice fire, set out our chairs, had these custom made rod holders a buddy of mine welded up from rod iron porch railing we'd drive way down into the sand, wade out chest deep to cast, then sit in our chairs BSing, drinking beer, even playing guitar, till the click click would get our attention. One of my favorite fish stories is one I call "Who caught who" about catching a Tiger late one night. Let's just say getting too drunk is not a good idea. Pier or Jeffy you can lay your big line out and then work your small line catching the smaller game fish, on the Gulf like Jacks or flounder. Another favorite was we'd go under bridges in the inlets usually as the tide came in. We had this small stainless barrel, we'd fill with salt water than get a hot fire going under it. That was a three way experience. We'd put a heavy line out for the big ones coming in following the tied eating the littler ones, a live shrimp on a slapper for Red snapper, and then use a chicken neck on a string to net blue crabs. The Blue crabs, we'd chuck in the barrel with the corn on the cob. I always kept wire strippers with me so I could cut the legs and strip the bones off and soak in hot butter. Crab, corn on the cob, and a cold beer, that was good fun. With someone almost always picking a guitar, we'd be almost "Jaws" party except we were a bunch of rednecks.
The point being, catching the big one It isn't going to happen every day. It takes a lot of patience which most of us don't have. Its best to keep yourself busy doing something else. A boat and a guide who knows where, increases your odds. On shore though, its not impossible.
Tj