Help! Compiler Error!

Hey guys,

i started today with unity and after i downloaded the tropical island demo because i wanted to edit it for my game, i wanted to test, how is it to "play" it. but i can't play it and it shows me "compile error ... fix it" or something like that. I found the line, where the mistake is (yes it stands in the error) but i dont know what to change to fix it the error is Assets/Scripts/UnderwaterEffects.js(23,46): BCE0022: Cannot convert 'UnityEngine.GameObject' to 'float'

and the line in script is that:

{

     water = FindObjectOfType(Water);
     if(water) waterLevel = water.gameObject;
 }

i hope i get a quick answer

greetz

ISIBOII