See section entitled on-campus jobs. Off-campus summer jobs in Hattiesburg are very competitive.
Lifeguards are always in demand, as are food service workers.
There are also many websites that can facilitate finding this kind of summer job. Check out Campstaff . Use your search engine to locate your favorite park. Most have on-line employment applications nowadays, like Cedar Point in Sandusky, Ohio. It's very possible to get this type of job by mail.