While Smoothhounds might the one of the better types of "swimming sharks" to keep. I would still recommend some experience with one of the benthic "Aquaria friendly" species - i.e. Bamboo(Chiloscyllium sp.), Epaulette(Hemiscyllium sp.), Coral Cat (Atelomycterus sp.), or Horn (Heterodontus sp.) - before attempting to keep one.
Also research about keeping sharks. These lots of good informative magazine articles written about keeping sharks. Also a couple books on the subject - such as "Aquarium Sharks & Rays" (informative, & easy to read, but tank estimates are too low -IMO) & "Elasmobranch Husbandry Manual" (Technical, and Professional geared - but also very helpful). Also online forums are nice place to talk with experienced on various "aquaria" sharks.
Also note - the term smoothhound - actually is used to describe - all the members of the family Triakidae (smoothhound sharks) which is covers some 9 genera, & over 3 dozen species - including the Leopard shark. And depending on the species - may require tanks/ponds/lagoons that ranges from 1,500 to more than 10,000 gallons in order to keep one of these species. "Smoothhounds" may range for about 3' long to 6' long(or more) in size.