I have a rather large and ungainly table on a web page, and I want to implement some way to make the information more accessible (http://www.diveadventures.com.au/pages/Group_Dep.htm)

I think there's a way I could implement searching or filtering boxes using javascript or similar which might improve the table, but I have limited experience coding with js.

Would this be simple to do? Or is there another method which might be more appropriate?

Thanks in advance

No, not javascript. Use a server-side language to generate the page. It's easiest if the data can all be in a database too.

(Looking at your page, this is a classic job for a DB-backed website.)

Here's a javascript solution where the user can sort any column without reloading the whole page: http://www.kryogenix.org/code/browser/sorttable/

A server-side solution will always be more reliable, though.