At first I was kinda siding with you, A3. But a lot of people have made some very valid points.
One counter argument that I was thinking is that if you catch the shark, that kind of puts its life-credit in your bank. But I thought about it for .5 second and realized that's a stupid argument.
One thing that I thought was that you could catch one, throw it in the tank (as a fisherman I love the idea of catching a fish and then keeping it as a pet!), and then when it gets too big catch it and release it again. Kind of like a fish rental.
That way you'd get your predatory shark, it'd be small enough for your tank, and then when it started to get big you take it back and set it free. No harm no foul, right?
But then, what if, since the shark had related humans and food, it bothered swimmers looking for an easy meal. It would scare the bejeebus out of people, not to mention if it actually bit someone!
So I feel for you, I really do. My impulsive nature knows where you're coming from. But in this hobby, we've gotta repress it, do the responsible thing, etc. etc. etc. I'd pass on it.
Send me a PM and let me know what you end up doing.