Long term it is best to grind out Angler’s to revered. It is in the southernmost zone of Pandaria. You can do 3x dailies for 500 rep each, 3 rare fish turn ins for 350 rep each (spinefish alpha, mimic octopus, flying tiger gourami), and the hozen peace pipe for 1000 rep each week. At revered you can unlock the Azure water strider mount for all your toons and that mount has proven time and time again to be useful across all expansions. Furthermore the angler’s raft you get by doing that rep grind once will be usable by any alt that trains Pandaren fishing skill to 1 at the trainer.
If you had an old Northrend alchemist, you can do elixirs of water walking. It is a Alchemy 400 recipe acquired via Northrend Alchemy Research, where you basically daily try randomly to discover it. Once you have it, you can fish up glassfin minnows in Crystalsong forest, make ethereal oil, then turn that into elixirs of water walking and mail those off to your alts.