I do like the amount of thought that was put into the homebrew, I must say. I'd like to see it cleaned up, maybe even fleshed out a little more thoroughly for us players that are passionate about our characters. Lol.
All in all, less repetition, a little more .. je ne sais quoi.. about the race on a more personal level to make you really WANT to play that race, and this is real good. Throw in a few maps, some monsters, items to to fill those item headlines, a short adventure, and this could easily be up there with the Tiefling, Dragonborn, and Eladrin books out there.
I must admit that it has my DM brain swirling with all the wonderful information you have on the different city locations and such. I do believe that the underwater campaign that my player has been begging for shall come... but not until I have chosen and "built" one of such cities. I look forward to coming up with history, NPCs, shops, landmarks, etc. I've built many a city, but none from the SEA floor up! HAHAHAHA.
Aria