Sometimes referred as the Profit Route or the Qufim Route, the Saltwater Skillup route can rake in a lot of gil, but can yield a lot of broken rods, lures, and mobs. Leveled Woodworking, Alchemy, and Cooking skills is helpful here.
This guide was derived from Kida's Final Fishing database and guide.
Level 1-10 - Port Windurst
Targets will be Cobalt Jellyfish and Bastore Sardine. Use Halcyon Rod and Sabiki Rig. Cobalt Jellyfish tends to have an item-like behavior. Save the sardine for used in making bait for later. Cobalt Jellyfish sells decently on the AH.
Level 10-39 - Qufim Island (Ice Pond)
During the day you should have little trouble from the aggressive Land Worms, due to parties chaining. At night, the Banshees will pop and things can get dicey, but those mobs have a sound aggro range of less than 5 feet and do not move very much. Cancel all the !!! since they are monsters. Start with Halcyon Rod and Lugworms, then change to Shrimp Lure at level 17. The targets are Yellow Globe (which also sells well on the AH), Tiger Cod (should be saved for cooking purposes), and Nosteau Herring.
Level 10-?? - Qufim Island (North Shores): With Halcyon Rod you should cancel all the !!!, since Gigant Squid will break the rod. I used Sabiki Rig for bait catching Yellow Globe (which also sells well on the AH), Tiger Cod (should be saved for cooking purposes), and Cone Calamary. NOTE: Goblins camp this area. There is no way to fish without getting agro unless you are high enough level to where you do not get agro.
Level 39-55 - Qufim Island (North Shores)
You have a choice of Halcyon Rod or Composite Rod with the Minnow bait. If you use Halcyon Rods, you must cancel all the !!!, since Gigant Squid will break the rod. If you use Composite or Lu Shang's, you can attempt the Gigant Squid, but expect line snaps with the Composite. The main targets, however, are Cone Calamary and Bluetail. Cone Calamary has an item-like behavior, Bluetails will have frequent rod movements. The main drawback to Composite Rods is that you can lose some Cone Calamaries with the too small message, and it is very difficult to land Bluetail. Save the Bluetail to make bait for later. Cone Calamaries are popular due to their conversion into Tentacle Sushi or Black Ink. At 48 you can either move to the south shore of Qufim or Buburimu Peninsula to target only the Bluetails with Halcyon Rods, canceling the !!! in the process.
Level 55-63 - Vunkerl Inlet (S) - Bridges
No mobs pop on bridges, but you may need sneak and/or invisible to get to the bridge after using the CA warp. Use Halcyon or Lu Shang's Rod and Crayfish Ball as bait. Cancel all the !!!, they are either mobs or Arrowwood Logs. Trumpet Shell is the new profit fish right now, ever since Wings of the Goddess came out - it is used to craft Carbon Dioxide, which is used to make Movalpolos Water. A stack of Trumpet Shell goes about 20k to 30k depending on server as of 3 April 2008.
Level 55-66 - Ferry Fishing
You must have a job that can cast sneak on the Selbina-Mhaura Ferry, it is the only protection from the Sea Horror. Blackbeard and Silverhook may hear through sneak, but their aggro range is small and are occasionally camped. You use Composite Rod and Sliced Bluetail and go after Bhefhel Marlins. This fish should be saved and traded to Zaldon for gutting, as you can get one of 2 different RareEx chart used in a mini quest (the odds are 1/30 for Pirate's Chart, 1/100 for Brigand's Chart). The Marlins do not stack. Silver Sharks will fight off a Composite Rod but not a Lu Shang's. At 61, switch to Halcyon + Sinking Minnows and only target Noble Ladies. All !!! with frequent rod movements should be canceled as they are rod snapping Titans.
Level 55-99 - Nashmau
Since this is a town, you never have to worry about mobs. From 55 to 86, use a Lu Shang's and a Shrimp Lure and target the eastern versions of Grimmonites and Bastore Breams. Unlike Sea Serpent Grotto, there is no Nebimonites to worry about. From 86 to 90, cancel all the ! and only target the !!!. Starting at 90, start using Lugworms as the bait and target Pterygotus. I NPCed all the fish to the nearby vendors.
Level 66-79 - Qufim Island (south shore)
The target is Three-eyed Fish with Composite or Lu Shang's and a Minnow. They will yield the !!!, the other fish that can be caught with Minnow will yield !, making these easy to point out. These fish are frequently used as guild point items and is required to trade in for rank promotion to Adept. You can also switch to Sliced Cod to target Black Sole, but only if you have a Lu Shang's rod and an Albatross Ring.
Alternative: Sea Serpent Grotto (Lake) with Lu Shang's and Shrimp Lure. Sneak/Stamina Fishing is required, as mobs can range up to level 65. You can get up to level 90 with Bastore Bream and Grimmonites, and make a killing off Nebs. As of March 2008, it is no longer possible to fish under bridges at the lake.
Level 79-96 - Qufim Island (north shore)
Use Lu Shang's Rod with Sliced Cod. The Cone Calamaries will target the bait but they are predictable. The main targets will be Black Sole and Gigant Squid. Gigant Squid do not stack, but are frequently targeted by cooks for a popular item called Squid Sushi, and can be made into Black Ink. Black Sole is also another popular item, as it is used in Sole Sushi.
Level 96-100 - Ferry Fishing
This is where the cheap Yew Fishing Rods and Meatballs are the best while on the Ferry. They can be purchased from the shop on the ferry very cheap, and if they break, you can sell it back and get a new one at a slight loss. There are a lot of legendary fish to target at this point, all of them do not stack. Make sure Zaldon guts every one of them, as some are required for the Ebisu Fishing Rod quest. Mooching and Serpent Rumors key items are required while on the ferry, along with the fishing rings.