You must have the audio files installed for this mod to work.
This mod adds a squid to the game with 30 health that drops iron and gold, and makes sounds from this video from Gamechap:
Here's the mod itself:
The squid is very rare, and if you happen to hear it while you're sailing through the ocean, it would be a good idea to find it and kill it since you can get iron and gold from it.
To install the mod, install Risugami's ModLoader, drag all the class files and the 'ocomo' folder into minecraft.jar. Drag 'retardedsquid' into .minecraft\resources\newsound
To install it for the server, install ModLoaderMP, and the mod itself into minecraft_server.jar. To play it on a server you have to have ModLoaderMP installed on your client as well.