The starting zone in BC, Hellfire Peninsula, has no water that I've found. The next zone, Zangarmarsh, has lots of lakes and new places to fish. There are ‘wreckage’ spawns which drop boxes of Elemental Blasting Powder and Fel Iron Ore (nice!). There are also pools of “Pure Water” in Nagrand which drop Motes of Water. I’m really pleased with these discoveries, because once again it validates Fishing as a viable way to get valuable crafting components. Previous loot spawns contained mostly potions and bolts of cloth, so the addition of new materials relevant to other crafters is a real bonus for fishing.
Primals (Earth, Fire, Air, Water, Mana, Life) are the new essences of the Outland. They are used very heavily in most professions, usually for rare or epic quality recipes. The upside is that they are easier to collect than essences, the downside is that the new recipes seem to use ALOT of them. It’s not unusual for a recipe to require 8-10 of various types. Because they drop frequently, I believe there’s going to be an active market springing from the buying and selling of them.
Just to give a rough idea of the drop rates involved, I usually end up with 5-10 motes when I go mining each morning (some earth/some fire). I’d guess they have about a 15% drop rate from Fel Iron Deposits, which seems to jive with Thottbot’s numbers. When I was killing Withering Giants in Zangarmarsh, I got 6 Motes of Earth. I would estimate that I killed less than 2 dozen giants, since I only needed 12 to complete the quest (I had to kill a few adds and pathers though). As you can see, they are fairly common compared to essence drop rates. Granted, you need 10 of them to create 1 primal, but it’s still easier than farming essences.
As for leveling up your fishing, that's going to take a good long time. Any of you who remember how hard it was to get the last few bits to 300, you'll pretty much be continuing from there. Right now I'm sitting at 304, I believe I was getting a skill point 10% of the time. It's hard to say because I was getting more unsuccessful casts, of course. Even with my Aquadynamic Fish Attractors I was getting 10-20% miss rate ("Your fish got away!") So don't plan to power up to 375 unless you want to spend many hours fishing :)