thats exactly right. you element isnt always based on your zodiac sign. in order to find your element you should try using them all and get a feel for whichever one you are drawn to.
remember no one can tell you what your element is. that is for you to find out on your own, after youve used them all.
so to answer your question, although your zodic sign dictates your element should be water, it is perfectly fine to be drawn to earth as well.