Don't get a leopard shark...PLEASE!! They are one of the most wrongly put animals in an aquarium. 6-9 ft in length, they are not bottom dwellers and they swim plenty. Nurse sharks grow to fourteen feet in length, yes, even in an aquarium. Most sharks don't even live that long in an aquarium.
On a lighter note, if you are going to build a 700 gallon tank for a shark, i would go with the Portjacksoni, or the Port Jackson hornshark. The absolute maximum length of five feet, and would require a chiller. More active than most bottom dwellers, and pretty impressive. Named a horn shark for the horns behind each pectoral fin. Don't touch, they hurt.
My shark of choice would be a black-tip reef shark. Of course, unless i have $100,000-$500,000 to blow on the several, several, several, several thousand gallon tank, it isn't going to happen. I would never wish to harm a shark in anyway. Just check out my signature.
Please do some serious thinking before purchasing any shark, and if you have any questions, please ask them. It is better to feel stupid than be stupid.
If you catch my drift. (And no, that is not an insult, just a cool saying)