Well its not exactly disgusting, because their diet is made of a lot of water. So most of what goes in, comes out. And the percentages of "fish pee" is at more like 0.000000000000001% So dont be all creeped out.
fish breathe water, and yes it travels through them. They poop too!
I doubt there are sharks close to the beach you are on, but the ocean has way too much circulation to even think about something like this coming near you.
