Deep-sea fishing rods differ from other fishing rods in that they are longer and heavier, with thicker eyes and angles. Deep-sea fishing rods are also treated to prevent saltwater damage, and their reels are equipped with lines that are longer and of greater weight capacity. All this is necessary because saltwater fish tend to live in deeper water and grow much larger than freshwater fish.
Not all fishing rods used in the sea qualify as deep-sea fishing rods. The term is reserved for the type of rod used to fish in deeper waters as opposed to those used to fish from the shore or a pier. Deep-sea fish such as marlin and some sharks can grow to over 1,000 pounds. For these larger trophy fish, rods are often custom-made for individual fishermen, and they need to be used with extremely heavy equipment. The casual deep-sea fisherman should be judicious in choosing a rod, even when fishing for species such as tuna or grouper, which can weigh hundreds of pounds.
Because deep-sea fishing rods are much longer and the equipment used with them much heavier than freshwater rods, balance becomes a much more important issue in the handling and casting of the rods. A simple test of balance with a deep-sea rod is to hold it out horizontally. If it tips forward or back toward the reel too much, adjustments must be made for efficiency and superior control.