Well, *technically* not any plant can be a perennial. There are true annual plants that have a natural life cycle of grow, bloom, set seed & die in a single growing season, and no matter how warm you keep it/them they won't live longer than one year.
But, as Lisak1 states, there are many perennial plants (those that live & grow for more than one year) which are 'tender', meaning they can only survive temperatures down to a certain low point before they will be killed & not able to recover (unlike a true perennial which will go dormant during cold weather, but come back from the roots when things warm back up again) Some people in cold areas will treat these like 'annuals' and just enjoy them for one summer, knowing that freezing weather will kill them.
What you need to do in order to decide if a plant will perform as a perennial in your garden is know your "Zone" & then check the information on each particular plant to make sure it is at least that hardy.
@420benz - your information is listed as you being in Georgia, hardiness zone 8. Any plant that is listed as at least 'zone 8' **should** come back for you year after year (I say 'should' because when it comes to plants, there is no guarantee! lol) If it's listed as zone 9 or 10, or 11, then no. This plant will not survive through your winters & come back next spring.
Now, just to complicate things a bit, there is also a 'heat zone' map which is different than a 'hardiness zone' map. Some plants don't perform well when it's too hot for too long & will actually go dormant in the summer, rather than in the winter. Some plants also actually need a cold period of dormancy in order to continue to survive & thrive. If these are in too warm/temperate of an area they will struggle and probably fail (at least prematurely)
Is any of this helpful to you? Do you have any more questions? Perhaps if you could give some more through description of your pond, garden, climate and what you're trying to achieve with these plants, people could give better advice, more specific to your situation.