Fire watcher here. Many ranged classes have an advantage in water (or classes with underwater speed/water walking) because melee classes lose their passive movespeed buffs once they hit it. Hunters and mages in particular can disengage and blink on the surface of the water, laughing at people while they still swim at them. A well placed warlock portal should have a similar effect, as well as any jump (a warrior should be able to keep most ranged close to him while theyre in the water).
Also get an anglers raft--- you can attack from it, and with ANY movement speed (passive or active) its faster than an epic mount easily.
Take advantage of the "phase" area by the ghosts in the cave underwater on the west side, you can often evade a zerg of people out for blood if you phase into the other area.
Edit: One item that was missed in the guide is the "aqua jewel" that increases swimspeed by 50%. Not as good as the swabby helmet, but as a hunter kiting a melee underwater hilarity will ensue.
If you're at the ship, picking off people, the ship has a weird shadow bolt it will spam you with if you are moderately far away. If you start taking massive damage, but there's no fire, you're too far. Move closer or just leave the area.
Several more items: Scuttler's Shell - Lowers your aggro radius immensely for mobs. As in you can ride right past the Yaungol on the bridge and they won't touch you. They drop from Ancient Spineclaws, and stack to a maximum of 10. Useful if you've bit off more than you can chew, just kite melee players to a group of mobs. Windfeather Plume - Increases your mounted speed. Good for chasing down people, or escaping when you see danger headed your way. They drop from cranes (elite and rare), and are BoA. Buff drops off if you go into fatigue water, otherwise lasts an hour. Golden Glider - Works much like the engineering glider, good for jumping off high places to either escape, chase someone down, or rush across the island (I like the area around Leafmender). Only 1000 timeless coins for a stack of 5, bought from panda child at SE corner of the Celestial courtyard. Faintly Glowing Herb - Maximum stack of ten, drops from ashleaf sprites. Like a HoT pot with now cooldown. 300k health over 10 seconds. They expire after a day, and the expiration for your entire stack is based off of your oldest herb, so destroy your stack at the beginning of your day. Strange Glowing Mushrooms - Maximum stack of 20, drops from Rock Moss and his Damp Shambler friends. Heals you 25% health over 10 seconds, and also re-energizes your special resources by 25%. Includes things like Demonic Fury, not just mana, energy, focus, and rage.
If you don't feel like making enemies in your own faction, you can also ask people if its ok to kill them. It's slower, but you don't have to worry about being jumped as much. If you're going this route, and you're announcing rares, let people know you won't be a danger. Some people won't believe you, and call you a liar or jump you, but it's not worth arguing with them. You won't be able to click on their portrait to whisper them, though. Make a macro: /run SendChatMessage("May I kill you for a bloody coin?", "WHISPER", nil, UnitName("target"))
And it's a lot less exciting, but depending on your server and your personal coin rate, sometimes its just as fast to trade kills with someone. If you both have like 5 level 90s, just keep them parked on or near the island, in a low traffic area not too far from a gy. One person use their bloody character to get the coins from the other person, then switch. You can only do this once a day (practically. maybe multiple times), because you have to run down the "recently sacrificed" debuff with each of your own toons while it is online.
And finally, I don't know if it was mentioned in the warlock section, but KB done by your pet do give you a bloody coin. At least they did when I tested with my hunter pet (it had the 'overkill' message in the combat log).