Well as I have stated numerous times. I was tullehar till the data was mistakenly lost and I can't log in. So im using Native Mod and help from Yogoda to start it off ^^
Ok, here is the skeleton for your mod 
http://dl.dropbox.com/u/4422249/fishmod.zip

menu (I have the French patch)


Hit escape in-game and it will bring a menu where you can choose a second form. I've done most of the complex scripting part, you don't need to understand all the code. Now you can quite easily add new forms, script abilities, and change the way they move.
Good luck !
I plan on adding way more fish and finding a way to give them abilities. Races will be through all of aquaria.
Oh and if Yogoda manages to find me, I noticed the fish player is invulnerable...though now that i've merged the project with native mod* maybe it will fix this.
*followed the native mod instructions XP lol but i need to restart cause the scripts latched on from native and its just native mod. i'm definitely pulling the maps from there. which is the base map script i need to drop that so I don't run into native's transport script.