Sure, but what have you done, and what are you stuck with? How complex do you want to get? http://answers.unity3d.com/questions/16193/free-roaming-ai.html http://answers.unity3d.com/questions/30527/underwater-implementation.html

Sorry, but your question is too broad, and this is not the place to ask for scripts. Unity Answers and its community is here to help you solve any Unity-related problems you have, not give away free code. If you don't know how to write code, I sugest learning Unity's Java Script (its really easy), but if you don't have time, or whatever, then you can try asking your question on the Unity Forums. I hope you can get an answer!

Also, use google. Do tutorials, and learn how to use Unity.

thank you sir.. I am currently planning and not yet starting with any script.. my plan is to do a 2d aquarium with a fish.. just thinking of what physics to change to make it feel underwater.. and how to make it look like water.. thanks again.

it's interesting, this question has me thinking about how to do it. I would use rigidbody's and turn gravity off. Have a look around at how other people are simulating fish, then start looking for code to move/animate fish with 'fish' behaviour, look into fog or shaders for underwawter effect. google and read alot, then practice alot.

http://forum.unity3d.com/threads/25248-3D-Fish-Tank-Aquarium-for-iPhone

http://answers.unity3d.com/questions/149557/aquarium-kinda-thingy.html

http://www.youtube.com/watch?v=q4Oted2VQog

http://activeden.net/item/aquarium-360-degree-panorama/2599299

nice resource you've got there sir.. that's a lot of help thanks!!!!

I just saw this video, perhaps it will help with your project =]

http://www.youtube.com/watch?v=Pd8ByJbVMmM&feature=autoplay&list=PL74F71544CE701190&playnext=2

fast forward to 1 min : 30 secs