Hello, me again! :-)
Personally I'd love to have a marine set up, the fish that you can get for them are amazing, awesome colours. However the price to set up, run, maintain and buy fish for is wayyyy out of my price range.
You can get sharks, i've got one myself in my tropical tank, however it's hardly Jaws like (heh) there's many varieties of sharks, and some that don't even look like them, infact mine looks nothing like you'd think a shark should look like!
Here's a Google image of what mine (Al- yes i name my fishies!) looks like.
http://www.gsas.org/Gallery/albino-shark-avene ll.jpg
Did you get chance to look at the forum I mentioned yesterday? There's also a fish index on there which tells you every variety of tropical fish going (the forum (i think) also has a marine section), it tells you which fish will be good tank mates for other fish etc, becuse you'd be devestated if one became fish food for another!