I saw a very interesting thing on the BBC show called Oceans today (Yes, I'm stuck in the binneland, so I stay sane by watching stuff like this..)
They were diving with blacktips in the Bahamas and had these plastic pouches with them that are experimental products being tested as shark-repellents.
Basically, when you squeeze the packet, it bursts open and as the liquid inside spreads through the water, the sharks move off, but the fish stay behind.
I hear you say, while sitting, nailed to your computer screen, "What's in the Pouch!? What could it be!?" Well, apparently sharks really don't like the stench of......wait for it.....wait for it......Rotting shark. Ha.
Weird, but it really worked....about 10 seconds after the guy popped one smallish packet, all the sharks high-tailed it out of there - there were a lot of them and they were feeding.
Now, I don't know how that would work with a Zambo or Tiger, hell-bent on taking a bite of you or your fish, and you definitely don't want to pop a packet in an angry Johnny's face as your last line of defense when things get wild. But it does pose interesting possibilities such as synthesizing and incorporating that specific scent into wetsuits or sunblocks and such. The downside of course, is that after a dive, you not only stink like fish and guts, but also of rotting shark. Yum.
My 2 cents....Buy yourself something nice