Good, but needs work.
This was pretty cool idea. It does need some work though. For your index, It's not really a good idea to put words over an image like that because it makes it hard to see. Type and images are both thought of as images/graphics and u don't carelessly put two graphics together because you won't be able to see it properly. I you are going to put type on an image try messing with the type till it works. For yours, i think u should try putting a drop shadow behind the type. It will make it stand out. (this only works in some cases, u have to play with the type to get it right.)
Also when you go to the under sea part i couldn't find a way to return.
I'm not writing this to make u feel bad or nothin' cause its actually pretty good. Just giving u ideas to help u improve it. :)