Just in case you are using a system with a browser that cannot support the java application served in the last page, I have compiled the program as a stand-alone version for various common operating systems. In eadch case, right click then 'save as' and put it wherever you would normally put applications. Remember to set execute permissions if you are using an OS that requires this.
Alternatively - and much easier in my opinion - first download Processing from www.processing.org, then download this sourcecode, open it an a text-editor, select all and copy, then start Processing, paste the code into the editor window and hit the run button.
(But easiest of all is to fix the problem with your browser!)
When you have finshed playing with the fish, click here for final remarks.