Oliver,
You're trolling here ;-)

Photos of sharks, yup. It's done. I've done it many times.

Piranhas? Heu, heu, heu.... First, it's not in the same place, then
it's something else... They will eat a cow in a matter of minutes.
Imagine an urban photographer and troller...

As for crocodiles, better from land, but watch it, they're ultra fast.

Have yourself a merry Xmas!

Marcel