Shoobie is a term used to describe a tourist who visits the seashore for a day (a daytripper), primarily to use the beach during the summer months.
Shoobie is used in the Southern New Jersey coast (along with other parts of the east coast), and resort towns in California. The term "shoobie" originated in the late 1800s, and it derives from daytrippers taking the train to the beach, with their ticket price including a boxed lunch packed in a shoe box. Later it was used to refer to anyone who brought a picnic lunch to the beach resorts. Either way, these daytrippers deprived local businesses of the revenue the tourists would have spent on food. Homeowners (whether year-round or seasonal) often walk to the beach barefoot or remove their shoes immediately upon reaching the sand. Similar terms are "Benny," which is mostly used in the resort towns of the Jersey Shore.
Shoobies are essentially a mixed blessing for local beach residents. They bring in enormous revenue during the summer months (less so if they bring their own food), but at the same time they add numerous obstacles and annoyances to day-to-day life. In that sense, shoobies are not unlike the tourists that descend on any resort area.
The term has also been mentioned frequently on the Nickelodeon show Rocket Power. The reference in the show is either to folks that wear their "shoes" on the "beach", as in SHOE-BEAch, or people who wear socks in their sandals. The term is also used to describe "day-trippers" on Nantucket Island. Slightly Stoopid & Toko Tasi recorded a song "Shoobie" which appears on Slightly Stoopid's Slightly Not Stoned Enough to Eat Breakfast Yet Stoopid EP