A school of fish

 A school of fish is when a bunch of them swim together all synced up,like they're in on the same plan.It's not just for looks-sticking close keeps predators confused,saves energy and helps them spot food.They don't talk it out;it's all fast instincts,watching each other to stay in line.Think sardines or herrings-they're champs at this,making it look like a flashy water dance.