NEW YORK (AdAge.com) -- Carnival Cruise Lines, whose recent marketing gimmicks have included a building-sized pinata and a blimp-sized beach ball, has scaled down its promotional visions a bit. Its new campaign brings sidewalk aquariums to six major cities. At each, cellphone-totting consumers can create their own digital fish on store-window interactive screens. They can also return to feed and otherwise commune with their new underwater pets. Carnival's chief marketing officer, Jim Berra, explains the project.