Hi Paranoid Peeps,
Stinky Goat, I think, is partly correct. Peeing in your wetty will attrack sharks but not because of the fear, although uric acid is released into the cells during times of fear. Peeing is the bodys way of removing the crap from your system, there are also minute traces of blood in urine which is what the sharks probably pick up on. They smell, I think it is 3 parts per million, of blood to water ratio and can follow that ratio of dilution from 3 k's away.
Mind you 3 parts per million of blood in water over a 3km path of say a path width of approximately (allowing for fanning from the source and a strong current and calm seas) 10m x 10m or 100sqm x 3000m gives 300,000 cubic metres or roughly 300,000 tonnes of water at 3 parts per million that would be approximately 1 tonne of blood or 1 cubic metre assuming that the specific gravity of sea water is 1.
I think i read somewhere that the adult male human body has around 5-6 litres of blood, that means you would have to drain the entire blood contents from 166 male adults

to attract a shark from 3 kms away or only 83 males from 1.5km away, 41 adult males and a boy at 750m, 21 adult males from 375m away, roughly 10 fully grown adult males from 180m away or 5 fully grown adult males at 90m away or almost the entire blood volume of 2 fully grown medium sized adult males at 30 metres away.
It's been a while since I was at the beach and noticed corpses completely drained of blood every 30m so you would probably be OK kiting around even with a vein cut and leaking moderate quantities of blood into the water.
Gees I'm bored! Don't ask me what possessed me to write this stuff.

This is of course all hypothetical and purely based on abstract thinking and probably bad math and maybe a bit of myth thrown in to spice it up and a lack of personal time on the water.
I say, pee in your wetty as often as you like especially in winter, it does more good than harm.

Unless of course the shark is only 3 feet away from your groin and you copped a cricket ball in the liver the night before.
Just food for thought. By the way, statistically, you are more likely to die in Australia from lightening strike or Bee sting than from Shark attack..... Just to put things into prospective.

Kite on!