Compiler Error

I'm currently using a freshly downloaded island demo file, on a mac os x running lion. Whenever I try to enter playmode, it says "All compiler errors must be fixed", or something along those lines, but when I go into the debug window, it gives this error: Assets/Scripts/UnderwaterEffects.js(23,46): BCE0022: Cannot convert 'UnityEngine.GameObject' to 'float'. and now its giving me this error: Assets/Scripts/UnderwaterEffects.js(1,18): BCE0043: Unexpected token: float. I've entered the file in DreamWeaver and it says there is a syntax error on line 1. Line 1 says: var waterLevel : float;

Any Help?